Omnichrome he cd laser manual
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Omnichrome he cd laser manual

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HeCd theory, operation, troubleshooting

HeCd theory, operation, troubleshooting

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Omnichrome he cd laser manual Omnichrome he cd laser manual Document Transcript

  • - TABLE OF CONTENTS 1. INTRODUCTION 2 1.1 Laser System 2 1.2 Laser Safety 5 1.2.1 Electrical Hazard 5 1.2.2 Radiation Hazard 5 1.2.3 CDRH Labeling and Caution 6 1.3 Unpacking and Inspection Instructions 8 1.4 Operating Instructions 9 1.4.1 Initial Installation 9 1.4.2 Remote Operation Interface 9 1.4.3 Normal Operating Sequence 10 1.4.4 CDRH Remote Control Connector 11 1.4. 5. Remote Control Box 122. THEORY OF OPERATION 15 2.1 Laser Head Theory 15 2.1.1 Plasma Tube Theory 15 2.1.2. Laser Head Electronics 19 2.2 Power Supply Theory 193. GUIDE TO TROUBLE SHOOTING AND REP AIRS 27 3.1 Diagnostic Flow Chart 31 3.2 AC Power on Status 32 3.3 Temperature Lockout Status 32 3.4 Laser Head Fan Status 32 3.5 Power Supply Fan Status 33 3.6 Cadmium Reservoir Heater Status 34 3.7 Low Output 3.8 Laser Output Fluctuates 37 3.9 Laser Beam is Distorted 384. LASER HEAD TEST, ALIGNMENT, AND ADmSTMENTS 415. POWER SUPPLY TEST AND ADJUSTMENT 476. LASER MALFUNCTION REPORTS 57
  • 1.0 INTRODUCTION1.1 SYSTEM PERFORMANCE Your Omnichrome Helium-Cadmium laser was developed for demanding commercial, industrial, and military applications where ruggedness of construction and reliability are essential. The laser plasma tube configuration is similar to that of a helium-neon laser where glass/metal construction has evolved into low cost, high volume manufacturable configurations. The laser plasma tube is of coaxial geometry with integral hard glass-metal frit sealed resonator mirrors utilizes cadmium of natural isotopic abundance .. High reliability and long lifetime are obtained by optimum choice of construction materials, careful design of the mechanical structure and of the cadmium vapor and helium pressure control circuits, and precise control of the manufacturing process. The Omnichrome Helium-Cadmium laser has been designed specifically for the stringent demands of the OEMllndustrial market place. Requirements ofthe UL, CSA, VDE and BI have been factored into the design. The laser as a component of your system will be readily accepted by the above laboratory testing companies. The center for Devices and Radiological Health (CDRH) requirements have also been met. 2
  • SERIES J9X OUTLINE DHAWING D D 1. SYSTEM MOUNTING HOLES REFERENCED WITH AN "A" ARE 1/4" (.250) .20 UNC (ENGLISH). 2. SYSTEM MOUNTING HOLES REFERENCED WI1H AN "8" liRE M5 )( 0.8 (METRIC). o " 8 li I) on to o " o .,:. N -.j- 0""" on ~ If) f-- ¢-.j rul oci J. INDICAlES COOLING AIR FLOW BEAM ct-- 3.12 I ~ 1-~---4-I11 A B • 0 -- - - - 2.12 DIRECTION. 4. X INDICATES OUTER SURFACE OF LASER OUTPUT WINDOW. WINDOW IS 1.12 o • A B .393 INCHES THICK. 5. INDICATED DIMENSIONS LOCATE SERIES 56X OUTLINE DRAWING uSER BEAM OUTPUT POSITION. ,G8- D 6. DIMENSIONS IN INCHES. ---p 6 00 ~lJ-1 . _2.-47 _0.00 I I ,.., 0 o o o " " ~ ON 0- III III " ..... " ID 0 ID N OJ) <0 IC 0": N I " N BEAM r. __ ~X==Ao t. ~"~~- -;-+I----~O+-.e=--------+-I--+- " A B A B 0-. -0-. - - 1 I -2.12 1.12 L-_ _·.,!:Bc......_ _ _ _ _ _ _ _ _ _ _ _ _.....l O.~5 SERIES 74X OUTLINE DRAWING D ~;~ £~J--.-..----F ~= 0 ~m ~~ II II 0,,11) co ~ ~ ~ J;7~~j1B 7 BEAM<t- 1.12 ~~.~B L-___ __________________________ ;_~_~-~-L12 ~J O.~5 SERIES 112X OUTLINE DRAWING1:1::lO~o.oo £_1--------------1o I I 0 0 0 0 It, 0 0 a 0:> III a ~ N 0 tf)~ N ~ <0 0:> ..t It)o on I ~BEAM <t _ J:5~-+-+-l­ I I t.50-~-- A B o • o • 0 B A L-________________________________________ II -1-50 4
  • 1.2 LASER SAFETYPlease read this section of the manual carefully before installing or operatinglaser.The protective housings of the laser head and power supply are not intended to beremoved by the user. It is recommended that any maintenance or servicerequiring access to the interior of the laser system be performed by anOmnichrome representative.Follow instructions contained in this manual for proper installation and operationof your laser.1.2.1 Electrical Hazard The laser head and power supply of this laser product contain electrical circuits operating at HIGH VOLTAGES. THESE VOLTAGES ARE LETHAL. If access to the interior of the laser head or power supply is necessary, but laser operation is not necessary. TURN THE POWER SUPPLY OFF AND DISCONNECT THE LINE POWER CORD. If access to the interior of the laser head or power supply is necessary while the laser is operating, EXERCISE EXTREME CAUTION TO AVOID CONTACT WITH HIGH VOLTAGES.1.2.2 Radiation Hazard This laser system is designed to meet all of the requirements of 21CFRI040.1 set forth by the U.S. FDA, Center for Devices and Radiological Health. A compliance repmi has been filed indicating the safety features of this laser. The laser is a Class III b device which indicates that it is capable of producing skin or eye damage if used improperly. 5
  • 1.2.3 Center For Devices And Radiological Health (CDRH)The following labels were designed to warn the user of potential LASER RAOiAnON - AVOIO DIRECT INVISIBLE lASER RAlJlAnON - IIVOIO EXPOSURE TO BEllM DIRECT EXPOSURE TO BEllM tESS THAN UESS THAN 150 MVII ClASS" b 5WI MW ClASS " b Hoed lASER PRODUCT Ht!Cd lASER IOOOUCTOne of these labels is located on the top rear of the Jaser head near the air outletfan. ~ (Dolp EX&iiB~ One of these labels is located on the output end of the laser head below the laser output aperture, and beam block. -O",,.,,·1jr,,»U ~ 1Jb:t) ~ jJ. • to ,I~f t r CHINO CALlh,)H~l)A lJl It " A III l "11 til" ·"ttl MODEL NO. _ _ _ _ _ _ __ SERIAL NO. _ _ _ _ _ _ __ MANUFACTURED _ _ _ _ __ THIS LASER PRODUCT COMPLIES WITH 21 CFR ,040 /IS APPliCABLE. MAOE IN U.S.A PAT. PEND. This label is located on the top rear of the laser head near the air exit fan. CAUTION- Use of controls or adjustments or performance of procedures other than those specified herein may result in hazardous radiation exposure. 6
  • DANGER LAIlll UIll4T miDI I!mI A",II IIIRECT DIOIII. Til eUMOne of these labels is located on the base plate, near the output end of the SAFETY RECOMMENDATIONS FOR USE OF LASER1. Never look directly into the laser beam.2. Set up controlled-access areas strictly for laser operation, and limit access to this area to persons required to be there and who have been instructed in the safe operation of lasers.3. Post warning signs in prominent locations near the laser area.4. Provide enclosed paths for laser beams when possible.5, Set up equipment so that the laser beam is NOT at eye leveL6. Set up a "flat black" painted target for the beam and shields to prevent strong reflections from going beyond the area needed for the prototype development. In addition to the above, please follow the laser safety control measure in American National Standards Institute Z136.1-1986. 7
  • 1.3 UNPACKING & INSPECTION INSTRUCTIONS1.3.1 Unpacking Omnichrome helium-cadmium laser has been carefully packaged for shipment. If any of the packing cartons have been damaged shipment, have the shippers agent present for unpacking. Unpack the units carefully and save the packaging materials for returning the units in case of shipping damage or for service at a later date. I f one of the units has been damaged or requires servicing for any reason, return both units.1.3.2 Inspection Inspect your helium-cadmium laser as soon as possible it is received. Look for dents, scratches or other evidence of damage. If you observe any damage, immediately file a claim against the carrier and notify your nearest Omnichrome representative. Omnichrome will arrange for repair without waiting for a claim settlement.NOTE: Prior to shipment, your helium-cadmium laser was carefully aligned and adjusted for optimum power output and reliability. Do not open the laser head or power supply or take any laser returned for realignment if tampered with. 8
  • 1.4 OPERATING INSTRUCTIONS1.4.1 Initial Installation After unpacking the laser head and power supply cartons, mount the laser head and power supply in a suitable location. Any operating orientation is allowed for Series 39X, 56X, or 112X laser heads or power supplies. Minor resonator alignment may be required for Series 112X laser heads if not mounted horizontally.NOTE: Ensure that the air inlet and outlet areas of the laser head and power supply are not obstructed. Connect the low and high voltage laser head cables and power cord to the appropriate receptacles provided on the rear panel of the power supply. Connect the other end of the low and high voltage connectors to the receptacles at the back end of the laser head. The plugs are unique and cannot be connected incorrectly. For the Series 112X laser heads, there are two power supplies and two sets of HV and LV cables. Be sure not to cross connect pairs of cables. A cable pair is comprised of a high voltage (4 pin connector) and a low voltage (16 pin connector) cable. Set the ON/OFF "master control" key switch on the power supply front panel to "On" and the "Laser Control" rotary switch to "SHUTDOWN" and then plug the power cord into an appropriate 11 OV AC wall receptacle. Tum the laser on using the "Laser Control" rotary switch. For Series 112X lasers, tum laser on using the two rotary switches on the power supplies. "ON" is designated as "OPERATE".1.4.2 Remote Operation Interface If it is desired to use the remote control capabilities of the laser system, the ac connector on the rear of the power supply can be connected as described in Figure 3. For operation in this mode the rotary switch is set to "OPERATE". This connector provides the electrical interface to a host system and provides for switching from "SHUTDOWN"(OFF)" to "OPERATE (ON) TO "STANDBY". In addition, it provides for an "OVERTEMP LOCKOUT" status signal. The standby function provides for extended lifetime of the laser when temporarily not in use. Recovery time from standby is less than two minutes. 9
  • 1.4.3 Normal Operating Sequence After the rotary switch (or remote switch) is switched to the "OPERATE" position a delay of approximately two (2) seconds occurs for filament pre-heat before the main tube current and cadmium vapor pressure circuits are energized. Then the main tube current circuit is energized and laser tube (incoherent) sidelight can be seen thru the laser head air inlet or outlet areas. The green and two yellow LEDs on the front power supply panel should be lighted indicating that the ac power, cadmium regulator, and helium regulator circuits are "ON" . After about two or three minutes from initial turn-on, blue laser light should be noted from the optical output aperture of the laser head. Power output is typically stable within five minutes after initial turn on. If the red panel light is ever lighted during operation or during turn-on,i, this indicates that the laser plasma tube is too hot due to blockage of the , air cooling duct (dirty air filter, etc.), or that the plasma tube is too hot to I, I immediately restart. In either case, leave the laser system "on" and check for air flow blockage. Within a few minutes the laser will relight and come back to full power operation automatically. Faster restart time is achieved with the laser turned "on" since the internal cooling fan reduces tube temperatures more quickly. To shut down the laser simply turn the rotary switch to the shutdown p"osition. Internal circuitry initiates an automatic shut down sequence which starts immediately. First, the cadmium reservoir heater is de- energized and the discharge current is reduced to 80ma. The fans continue to run during this phase and the green AC power indicator light stays on. Some lasers continue to lase at lower power and some have no emission at this point. Second, at 2 minutes 17 seconds after the key switch is turned off the discharge current turns off. The red "Over Temperature" indicator light turns on at this point indicatingthat the plasma tube is too hot to restart. The [an in the laser head continues to operate for another 35 seconds and in some situations will provide sufficient cooling to allow the "Over Temperature" indicator light to go out. The fan in the power supply shuts off at this time. The green AC power indicator light is on during this phase. Third, at 2 minutes, 51 seconds the AC power is turned off completely. All indicator lights and fans are off. To restart the laser at this point, turn the rotary switch to operate and observe the red "Over Temperature" indicator light. If it is off, the laser will start automatically. If it is on, leave the rotary switch 10
  • on to allow the fan in the laser head to cool the tube to a temperature which is acceptable for restarting purposes. The normal internally controlled start up sequence will only start if the red "Over Temperature" light is off. Note: When operated on 50Hz power the time from switch off to the end of the first phase is 2 minutes 44 seconds. The time to the end of the second phase from switch off is 3 minutes 25 seconds. I WARNING: The key switch is for emergency shutdown of the laser only. DO NOT ./ USE THIS SWITCH TO SHUT OFF LASER EXCEPT IN AN _ EMERGENCY. However, for safe operation, please tum key switch to "OFF" and remove the key after the laser has shut itself off. lAA CDRH Remote Control Connector This connector provides access to the control circuit for the High Voltage supply for emergency shut down. It should NOT be used for every day tum off purposes. NOTE: (If external control of tum on, stand by, and shutdown is required see Figure 2, Section lA.5 of this manual for the schematic for the 9 Pin AC Input Connector). The CDRH remote control function appears on Pins 13 and 14 of the 16 pin Amp Inc. connector. It is the middle of the three connectors at the rear I of the power supply. A jumper is installed at the factory which must be I " removed to gain control of the High Voltage circuits. When these pins are disconnected there is no High Voltage to the laser tube and therefore no lasing is possible. Ifthe two pins are reconnected after a "Safety Shutdown" the discharge will only restart if the red "Over Temperature" light is out. If it is on, simply allow the fan in the laser head a few minutes to cool the plasma tube to an acceptable temperature to allow a restart."I - Please note that pins 13 & 14 control the main Solid State Relay in the Power Supply and carry < 25 rnA. However, these circuits are common I with AC line and require isolation from chassis or any ground. An~1 insulated switch or relay should be used to open or close these circuits. Due caution should be exercised to avoid any bodily contact with these circuits due to the possible shock hazard while the supply is energized. 11 - . -~
  • 1.4.5 Remote Control Box Via 9 Pin Connector THE ROTARY SWITCH ON POWER SUPPLY MUST IN THE "OPERATE" POSITION FOR REMOTE CONTROL LASER. Any of several configurations of remote control are available using the 9 ACIREMOTE connector on the rear of Model 100 power supply. If the remote control will be located less than 15 feet from the power supply, a simple remote rotary switch is possible as shown in Fi gure 2A. If the remote control will be more than 15 feet, it is recommended that switching be located near the power supply to reduce EMI pickUp in the switch lines. Pins 1 & 5 must be shorted to "OPERATE" the laser. Opening pins 1 & 5 will cause laser to "SHUTDOWN". If pins 2 & 6 are shorted at the same time pins 1 & 5 are opened, the laser will go into the "STANDBY" mode. Remote control may be effected by connecting two mechanical relays with normally open contacts, with one relay for each circuit (1-5 and 2- 6). Mechanical relays are available in type packaging that will operate from logic levels. One type is Magnecraft PfN WI71 DIP-7. The pin 1-5 circuit may be controlled with a solid state relay containing an and a light sensitive This require less than 100mA, AC. The triac should have at least a 200V rating (for 120V line). Both of the above circuits are at LINE POTENTIAL. They must be isolated from ground and each other, or any other circuits.Note: If the Remote Control Cable is greater than 2 meters in length, install an emission indicator light in the remote control box. 12
  • Customer Supplied IFIGURE 2A. I For Remote Operat ion I I FACTORY INS1ALLED JUMPER I ~REHOVE FOR REMOTE OPERATION 123 I o~o ° ~ a--==t I-SHU1DOWN 2-0PERATE Qo ( .. 6-~r=t: 3-STANOBY .. Of--.- - - - - - - - - ~---------------------- 5 !17 VAC NEUTRAL 8 2P 3T Switch I CHASSIS GROUND EXTERNAL I In <;I ~ y. .rot-------- TEMP 117 VAC HOT 7 ~~~KOUT ~~~~~~_______ ._________ I· ;>------------ I 3 -1 OIALIGHT 521-9240 OR EDUIV. I 330 OHM lAC LINE ICORD I NOTE: FOR RADIATION SAFETY CONTROL PER BRH REGULATIONS SEE SECTION 4.4FIGURE 2B. ~f------------- 5 1 2 3 L-Qf-------------REHOTE i-SHU1DOWN -------- °fo ~i)~--------- 6CONTROL 115 2-0PERATEOVER ft 15 3-STANDBY VAC }----------- 2FROM LASER. HO AC LINE N 0FIGURE 2C. OPERA TE:ENERG I ZE S . ~!.14 2 SHU1DOWN: OPENS. 2 ~~7-.-B-------------------­ 6 STBY: OPEN B, ENERG I ZE C. r---~~ HAGNECRAFlFOR OPERATION OF ~L14 A IS COHMON. W171DIP-7 L-or-7_,_8_ _ ___LASER FROM TTL 5LEVELS. C cr----------------------~ .------...... MAGNECRAFT 8 ... W171DIP-7 ANOTE: AMP PIN 606181-1 FEMALE SOCKETS USED IN 9-PIN PLUG. 13
  • 14
  • SECTION 2.0 THEORY OF OPERATION2.1 LASER HEAD THEORY Omnichrome helium-cadmium lasers corne in four frame sizes: 39cm, 56cm, 74cm, and 112cm. All Omnichrome helium-cadmium laser heads are made up of a plasma tube, resonator structure, head electronic printed wiring board, housing and cable assembly. All models of plasma tubes are similar in both design and theory of operation and all head electronics are identical excepting a few component differences. The primary differences between various models of laser heads are in the resonator structures and housings. 2.1.1 Plasma Tube Theory A typical Omnichrome He-Cd laser is shown pictorially in Figure 3. The main features of the plasma tube are identified in this picture. Omnichrome helium-cadmium lasers are positive column metal vapor discharge lasers using cadmium of natural isotopic abundance as the optical gain medium and helium as the start gas and cadmium excitation medium. Cadmium is stored in a reservoir near the anode end of the plasma tube and heated by a combination of internal and external means to be a temperature near 250 C producing a few milliTorr of cadmium vapor pressure in the reservoir. The helium pressure in the plasma tube is a few Torr. Cadmium vapor is ionized in the discharge capillary and transferred the reservoir to the cathode end of the capillary by cataphoresis at the rate about 1 milligram per hour. Within the capillary Penning ionization of the cadmium atoms by metastable helium atoms produce the necessary population inversion to produce optical gain at 441.6 nrn or 325.0 nm. The output power and optical noise of the He-Cd lasers is strongly affected by plasma tube current, helium pressure and cadmium pressure. Regulation circuits are provided in the power supply to ensure that an three parameters remain constant during the lifetime of the laser. Plasma tube ignition is provided by a voltage multiplier module within the power supply. The main discharge circuit is a switching 15
  • ANODE MIRROR FLANGE(HIGH VOLTAGE) DANGER CA TAPHORET I C CONF I ""-"LA""L 1------- CAPILLARY CADMIUM RESERVOIR AND EXTERNAL HEATER MAIN DISCHARGE CAPILLARYPLASMA TUBE TEMPERATURESENSE DIODE CATHODE(NORMAL + SPAHE) HELIUM PRESSURE REGULATOR ~ _ _ _ _ _ WITH HIGH PRESSURE RESERVOIR CADMIUM CONDENSER SECTION AND REMELT HEATER ---------CATHODE CONNECTIONS(NORMAL + SPARE) ~iII!S~ _ _ _-CATHODE MIRROR FLANGE (OUTPUT END OF TUBE) FIGURE 5. PLASMA TUBE SCHEMATIC 16
  • inventer type providing a regulated tube current of 100 mAo Switching frequency is 20KHz. Helium pressure within the plasma tube is regulated using a closed-loop control system which maintains helium pressure within 1% of set values. Heat loss type sensors within the plasma tube are used to sense both helium pressure changes and ambient temperature changes. These sensory signals are then used to control the rate of flux of helium from a side arm reservoir into the plasma tube. The time constant for this circuit is of the order of one hour. Helium demand by the plasma tube is indicated by the yellow "HE HTR" light on the front panel of the power supply. HELIUM PRESSURE SHOULD NEVER BE ADJUSTED USING THE POTENTIOMETER IN THE LASER HEAD. Plasma tube voltage is a sensitive measure of the cadmium vapor pressure within the discharge capillary of the plasma tube. Plasma tube voltage is used in a closed loop feedback control system to regulate the amount of heat provided to heater bands around the cadmium reservoir near the anode of the plasma tube. Power to the heater is commutated at the line frequency using a triac control. The duty cycle of the cadmium heater is a maximum of about -M% during laser tum-on, and about 40% during normal operation at;, normal ambient temperature conditions (75°F). Adjustment of cadmium pressure is performed using potentiometer in laser head. High tube voltage corresponds to low cadmium pressure, low tube voltage corresponds to high cadmium pressure. Time constant for this control is about 30 seconds. The normal operating sequence for the plasma tube is described with reference to Fig. 3. When the power supply is switched on, power is immediately supplied to the normal tube cathode (6.2VDC AT 1.8A) for about 2 seconds. If the plasma tube is at or near room temperature as sensed with the tube temperature sense diode (>.5V Across diode), the main tube current circuit is energized providing up to 27KVDC to the anode of the plasma tube. Ignition occurs immediately and a stable discharge of 100mA is maintained from the anode through the cataphoretic confinement and main discharge capillaries to the normalcathode. If the plasma tube is off but remains too hot (.5V across diode) due to recent operation of the plasma tube, the main discharge circuit will be inhibited until the plasma tube temperature decreases to a suitable value. If the plasma tube is operating and the temperature sense 17
  • diode voltage drop decreases below 0.2SV due to excessive ambienttemperature, air flow blockage, or fan failure, the main discharge circuitwill shut down. all these cases where the tube sensediode indicates overternperature conditions for the plasma tube the"OVERTEMP LOCKOUT" LED on the power supply will be lighted.The tube anode voltage after ignition is typically about 1300 volts forSeries 39X and 2000 volts for Series 56X plasma tubes.As soon as the 100mA discharge is established, power is supplied to thecadmium reservoir heater (SVAC at 3A). The power to this heater iscontrolled by a triac commutating circuit which regulates plasma tubevoltage. During initial warmup circuit operates at the maximumduty cycle about 80%.As the temperature of the cadmium reservoir begins to increase, thecadmium vapor pressures increases and is drawn into and down the maindischarge capillary toward the cadmium condenser section of the plasmatube.After about two minutes from startup the cadmium vapor pressureincreases enough to cause the plasma tube anode voltage to begin todrop. Since anode voltage is a very sensitive measure of cadmium vaporpressure in the capillary, it is used in the cadmium reservoir heaterregulation circuit to regulate cadmium vapor prcssurc. Within about fiveminutes from startup the anode voltage stabilizes to its normal operatingvalue which is about 9S0V for Series 39 and 1650V for 56tubes. After stabilization of the tube voltage the duty cycle of thecadmium reservoir heater is in the 3 S to 40% range if the ISadequate.Tube voltage regulation accuracy is usually within +2 or 3 volts. NOTE:If AlC power to the laser is interrupted for more than about 40ms theplasma tube will extinguish. Ifthis occurs while the tube is hot, the tubewill not immediately reignite. The tube temperaturesense diode inhibitsplasma tube ignition until the diode voltage drop increases above aboutSOO mY.The helium pressure regulator assembly is a side appendage to theplasma tube. It contains thermistors used to directly measure the localhelium pressure, a high pressure helium reservoir, a temperaturedependant permeable membrane separating thecma tube from thehelium reservoir, and a heater to cause transfer of helium from the 18
  • reservoir into the plasma tube. The helium pressure regulator and its control circuit operates totally independently from the remainder of the plasma tube. time constant for helium regulation are hours so that nothing rapid is occurring with this device. CAUTION it is important not to adjust the potentiometer 8 the laser head since can cause the plasma tube helium pressure to increase with a few hours. But the pressure cannot be caused to decrease in so short a time. 2.1.2 Laser Head Electronic~ Series 39X and 56X laser heads have a single printed wiring board and harness assembly. Series 112X laser heads have two iltcd wiring boards and two harness assemblies since they are made up of two Series 56X plasma tubes. The only component variation between laser head printed wiring boards and cable assemblies is R19 on WB3. R19 is 21K for Series 39, 13,.3K for Series 56X and 12.lK for Series 112. This resistor sets the plasma tube anode voltage adjustment range of the potentiometer R2. On the rear panel of each Series of laser heads is a set of test points which allow the easy measurement of several key operating functions of the laser head. The blue test point is chassis ground. The black test point is circuit ground. Between these two test points can be measured the tube current, It, where 100mA of tuhe current equals a 100mV measurement. Between the black and red test point can be measured the plasma voltage, Vt. And black and yellow test can be measured the helium pressure regulator reference voltage, Vr. Using the tube anode voltage and adjustment potentiometer, R2, a wide range of laser head performance conditions can be adjusted. Be sure not to adjust the helium pressure regulation potentiometer, RIg, by accident. Maximum laser output is achieved at about 950V on Series 39 and 1650V on Series 56 and Series 112 laser heads. Variations in the optical noise amplitude and spectrum can be obtained by adjustments on anode voltage using R2.2.2 POWER SUPPLY THEORY In the Omnichrome He-Cd laser power supply, there are three separate control loops: Tube current, Cd pressure, and He pressure. 19
  • 2.2.1 Tube Current Loop Tube CUlTent loop utilizes a Pulse Width an S02524J as the main element in the loop. This I.C. produces a variable pulse width signal to control the Switching transistor, Q2. Isolation of Q2 Base signal is necessary due to the different potentials present. This is effected by the use of a fast optocoupler, a 6N 136, Q24, which contains a LED, a photo diode, and a transistor. The signal out of Q24 feeds an emitter-follower, Q23 and a pull-up resistor, Rl16, to supply sufficient drive to saturate Q22. Now, Q2, the Switching Transistor, has its Emitter returned to the common of a +/- 9V Supply formed by CR40, C3, &1 C4. When Q 22 is OFF the Base ofQ2 is pulled up toward +9V by RI13, 82 Ohms. When Q22 is ON, the Base ofQ2 is pulled down toward -9V thru Rl14, 12 Ohms. A divider is formed by Rl13, & Rl14 so that 02 Base does not reach its Zener voltage value. By driving 02 Base negative, a faster, more complete turn-off is realized. The main H. V. Bridge, CRl, feeds two 1400 ufcapacitors, CIa & Clb, and is current limited by a 1 Ohm resistor, R 1. The positive side of the capacitors go directly to the center tap of the H. V. Transformerprimary, T3, and the cathode of CR9. The negative side feeds the Emitter of 02, with its Collector connected to the Anode ofCR9, a lN3893R, and one end of the Inductor, Ll. When Q2 is ON, it charges L 1. When Q2 is OFF CR9 conducts, protecting 02 and completing L 1 Since there is no significant filter capacitor after Ll, it operates as a current source for the Inverter transistors, 03 & Q4, and is connected to Q3,4 Emitters, and returns to the circuit Common of US. The Inverter transistors are driven by the S02524 I.C. thru Q8, which drives U4, a Flip-Flop 1. e. (7474). This, then, delivers two 50<Yo squarewave signals, 180 degrees out of phase, to the SG3627 I.e. which supplies these signals, with current-limiting, to the transistor Bases. The 7474 and 3627 both use +SV supplied by U3, a 5 volt regulator I.C. The 3627 I.e. has two 2.7 Ohm resistors to limit the drive current to the Inverters. R2S, 34 & C14, 17 cause the Bases of Q3,4 to go negative during turn-off, insuring a fast, clean turn-off. 20
  • The Switcher, Q2, operates at 40 KHZ. The Inverters, Q3, & Q4 operate at 20 KHZ. The frequency is determined by C 11 and RIll, may be checked POWER SUPPLY CHECKOUT T3 is a step-up transformer to develop the H.V. required by the Plasma Tube. T3 feeds the H.V. Module which contains a diode bridge, a i1lter capacitor, and a Start-Voltage multiplier to develop the very gh voltage required to start the Plasma Tube. When Tube is lit, current flows thru the tube and to the chassis thru the filament circuit. From the chassis the current flows up thru R48. 10 Ohms, then thru the overcurrent circuit and back to the I-LV. Module, pin 5. The I.e., ARl, contains four Op-Amps, one of which acts as the Tube Current sense. U7 has a regulated +5V output at pin 16, which feeds a divider, R39 & I R40, modified by R82. A reference voltage is derived, l+I-.(nV, to feed ARl, pin 2. Pin 3 sees the voltage drop across R48. Thus, 1 if pin 3 is less than pin 2, the output at pin 1 goes low, near OV, and supplies no current to Q9 thm R52, 1 390 Ohms. This allows U5, 1 SG2524, to tum ON the Switcher, Q2, tomaximum duty-cycle for maximum current to the Inverters. This supplies full current to the Plasma Tube. If pin 3 of ARl is more positive than pin 2, then pin 1 will go high, causing maximum drive to Q9, reducing the Switcher duty-cycle to mll1l1TIum. the voltage across is I I the circuit will balance and maintain this condition. (100 mA) This, then, describes the Tube Current Control Loop.2.2.2. Cd Pressure Control Loop (Tube Voltage) Now, with a stable Tube current flowing, the Tube voltage, may be used to indicate the relative Cd pressure. More Cd means a lower Tube voltage and less Cd means a higher Tube voltage. At pin 1&7 of the H.V. Module appears the tube voltage, measured just before the Start Multiplier. This start Multiplier has a constant 10 to 15V drop and for practical reasons can be ignored. Pins 7&1 are connected to a 10 Meg, H.V. resistor and thru R19 to Circuit Ground. The voltage across R19 represents a fraction of the Tube voltage. It is applied to the second section of ARl, 1 pin 10, acting as a voltage follower to avoid loading of R19 signal. 21
  • In the laser head on WB3, is another +5V regulator, Ul, supplying a. constant 5V reference to a divider formed by Rl, 2, & 3. R2 allows adjustment ofthe voltage applied to pin 12 of ARl on WBl, which results in setting the Tube voltage to an optimum value. (Actually sets Cd Pressure).C23, R53, C26, R57, & C27, act as a lead-lag network to compensate forthe Thermal Lag in the Tube and Cd Htr assembly. U7, another SG2524is again used as a Pulse Width Modulator. but this time at 120 HZ.The AC applied to CR19 is sampled by two diodes. CR20 and CR21.They deliver a full-wave signal to Q 12 which tums-ofT only at the cross-over points of the wavefonTI. R45 and C44 help remove any RF thatmigbt affect circuit operation. R4! insures tbat the transistor Base willreach ground potential at tbe cross-over points. R44 cbarges e21 whenQ 12 is OFF. CR24 allows a full cbarge of C2l. CIU5 supplies anegative pulse to pin 3 of U7 each time Q12 conducts. Tbis serves tosynchronize the 2524 to tbe line frequency.If tbe signal at pin 10, ARI (Tube voltage) is higber tban tbe Ref signalfrom WB3, R2, then pin 14 of ARI will go low and increase tbe Cd Htrduty-cycle. This will cause the Tube voltage to begin to drop. When theTube voltage, at pin 10 equals the Ref voltage at pin 12 then the circuitwill balance and maintain a constant Tube voltage (Constant CSDPressure). It should be noted that the thermal response is slow and 2 to 3minutes will be required for a stable Tube voltage, after IU is adjusted.The triac on WB2 is the actual controller of the Cd HiI current. Eachtime the AC waveform feeding the triac crosses zero, the triac turnsOFF. How soon it is triggered ON during each half-cycle is dependenton U7 and the difference between Tube V arid the Cd refV. A resistordivider of R51 & R54 clamp pin 9 of U7 thru CR26, limiting themaximum Cd Htr duty-cycle to approx. 80%. This is necessary to insurereliable triac triggering.C31 is charged by R67 during the off-time of Q15, with CR28 providinga full charge each time. When Q15 conducts, C31 delivers a negativepulse to the triac, Q 1 on WB2 thru CR29 & CR30. These diodes reducethe peak amplitude and tend to reduce RF contribution to the triggeringof the triac. At turn-on of the system, the Tube voltage is always high,since no Cd is present. This turns ON the Cd Htr to maximum (~80%)and continues until the Tube voltage drops to the set value. 22
  • 2.2.3. He Pressure Control Loop Inside the Plasma Tube are mounted four thermistors. Two for control and two for spares. One thermistor is used mainly to sense and the other to sense temperature. These thermistors are nominally 5000 Ohms at 25 degrees C. In the circuit, one thermistor is operated at approx. 30 mA, causing it to heat up considerably, lowering its resistance, since it has a negative temperature characteristic. The other is operated at about 3mA, with very little heating effect. Both thermistors sense temperature, but the 30mA unit also senses He density by heat-loss. The thermistors are connected in a bridge configuration, with a voltage comparator, an LM311, with one input looking directly at the 30mA thermistor thm R8. The other input sees the 3mA thermistor ihm RIO and a network formed by R6, R7 & R9 (to compensate for difference in thermistor voltages). In effect, bolh thermistors respond to temperature, but one responds to He pressure, as well. In this manner we can control He pressure over a useable range of temperatures. To balance the thermistors at a given He pressure, the voltage applied to the thermistors from U2 on WB , can be varied by R 18 over a range of S.OV to lO.2V. Since the 3mA thermistor is not materially heated, it responds in a positive manner to the applied voltage. The 30mA thermistor, however, follows immediately in a positive manner, but then in a negative manner as the thermistor up (negative characteristic). This takes a minute or two to stabilize. By carefully setting RlS, a good balance can be obtained at a given He pressure. The output of the 311, ARl, WB3, 1 drives Q 1 & Q2 which drive the Htr triac, Q2, on WB2.2.2.4. Line Fault Relay In the event of a brief Line Power loss, the danger of Power Supply failure is great. The line Fault Relay helps to prevent this failure mode. Without the Line Fault circuit, suppose a line drop-out of a few seconds occurred. The Tube goes out in about 60mSec, leaving approximately 80 Volts on the main capacitors. The low voltages will go to zero. When the power returns, the low voltage will stmi to rise, taking about a 100 mSec or more to reach the safe operating range. This means that we are powering up the main circuit with 80V still on the Switcher and 23
  • Inverter transistors. Q2, 3, & 4 are not being fully turned-on during this period, and the safe operating area of the devices are being exceeded! Now, with the Line relay circuit in place, relay will drop out after about 40 mSec. This disconnects the SSR and puls a 10 Ohm resistor across the main capacitors. Also, the filament delaycap, C9 is discharged. CIon the Line Fault board is discharged. When the line voltage returns, a delay of about 112 to 1 Sec before the Line Fault relay pulls in. This allows the main caps to completely discharge before allowing supply to come ON. After the delay, the relay pulls in enabling the H.V. SSR and the filament delay, of 2 to 4 Seconds. The H.V. SSR cannot be energized till after the filament delay. This insures that the low voltages will be up and the transistor drive is at full power. U4 holds off Q27 during filament delay, thus inhibiting K2, FI.V. SSR. Failure of the Power Supply due to Line dropout is virtually eliminated.2.2.5. Shutdown Timer The Plasma Tube has internal mirrors that would be damaged if Cd is allowed to collect on them. In the Anode end of the Tube is the usual confinement section to prevent the flow of Cd toward the Anode mirror. However, this is only true while the Tube is ON. If the power is cut-off, (plug-pull) then a small quantity may get on the mirror. Repeated hot shutdowns of this kind can seriously shorten the useful life of the Tube. A timer I.C., CD4060BE, is employed to avoid the problem. Plugging in the line cord energizes the Line Fault relay, ON the toggle switch applies AC to WB 1, 1 4. This charges up C35 to approximately 22V. VR2 regulates at lOY. CR37 allows to applied to pin 16 ofU2, Q3, 21, 28, 29, pin 12 reset), and Q4 thru RI08 allowing enabling of Cd control circuitry. In the reset mode, U2, pins 1&3 are low, turning OFF Q3&I28. This lets Q21 &129 to turn ON and energize K2, the low voltage SSR. Power is also applied to Q25 collector. Q25 is dependent on Q26, 27, & U4 before any drive can be supplied to K2, tLV.SSR. Q25 will be turned ON when the filament delay is finished. The Laser is operating and the toggle switch is turned OFF. C35 discharges, CR37 decouples, reset is removed and the Timer starts counting Line pulses (60 HZ). Q4 turns OFF, removing power from Cd controller circuit and the Tube current is reduced to ~82 rnA. The Timer will run for 216" before pin 1, U2 will go high, turning ON Q3, turning OFF Q21 and removing power from Q25. This turnsOFF 24
  • K2, H.V.SSR and the Tube goes out. Timer continues to count to 251" when pin 3 goes high where Q28 goes ON and Q29 goes OFF, removing drive from K2, L.V.SSR. At this point, all power is , and the system is shut down. The above sequence allows the to be cut-off, the Tube current reduced to 82mA, and time for the Cd to leave the Tube bore prior to the Tube cut-ofT. This reduces the chance of any CD getting on the mirrors.2.2.6. Cd Inhibit Circuit Q14 senses the presence of Tube current in ordcr to enable to Cd controller, U7. This prevents Cd build-up in the Tube in case it docs not lite. The Cd htr is also inhibited during the shutdown sequence.2.2.7. Temperature Lockout Circuit A diode, CR2, is mounted directly on the Tube body to sense temperature. The voltage drop of this diode is about .6V at 25 C, and drops with an increased temperature. The diode is fed with approximately 1 mA from U7, pin 16 (+5V Ref) ihru R72. This voltage is sensed at ARl, pin 5. A voltage divider, R70, R76, applies W.53V to ARI, pin 6. As long as the diode voltage is below .53V, the output of ARI, pin 7 will go low, ~~O V, cause Q17 and Ql1 to turn ON. Q17 sends an overtemp signal to 13, pin 3, and Qll resets Q4, removing drive from Q27 and turning OFF K2, H.V.SSR. This condition is cool enough a safe restart. When the Tube lites, Q16 senses the Tube current and parallels R76 with R73, changing the Temp Ref to .25V. This allows the Tube to run hotter than it can safely start. Say the Tube is operating, the temp diode is at .3 8V, and there is a brief power interrupt. The Tube goes out. Q 16 turns OFF, raising the Ref to .53V again. Now the povver resumes, hut an oveliemp condition will exist because the diode voltage is less than .53V. When the Tube has cooled to a safe temperature, it will automatically start. If the fan were to fail or the air circulation in the head were blocked the diode would heat up until the diode voltage goes below .25V. This will again trigger the overtemp condition In this manner, the Tube is not allowed to start hot nor allowed to overheat to a dangerous level. 25
  • 2.2.8. Overcurrent Lockout The return from the Module, pin 5, goes thru and R12, 1. The R8, R9 combination allow approximately 114 mA to flow before turning ON Q4 an Q7, triggering the regenerative switch, Q5 and Q6 which locks-up, resetting U4, WBl, again turning II.V. and the Tube OFF. The circuit will remain in the Locked-up mode until the AC cord is removed for about 3 Sec, after which the circuit resets automatically. lfthe overcurrent still exists, then it will lock-up again.2.2.9. Filament Voltage Regulator Ulan is the filament regulator. The filament voltage, at VB 1, 19, may be set with R2 on WB 1. The nominal setting is 5.55V. It is measured against Chassis ground. This insures Low-Noise operation over the full line-voltage range.2.2.10. StandbyMode Standby is initiated by opening the jumper from J3, 1 to 5, and connecting D, 2 to 6. Opening 1-5 turns the Cd Htr off and reduces the Tube current to 82 rnA. This also starts the Shutdown Timer. However, connecting 13, 2 to 6, inhibits the Timer and allows the Laser to run in Standby for an extended pcriod oftimc. This can extend the lifetime or the Tube by not using Cadmium during Standby. The Timer counts the line frequency and this signal appears across RI07, a 16V half-wave pulse. Shorting 13, 2 to 6, shorts Rl 07, thus the Timer does not count. In the newer model of Power Supplies, a rotary switch replaces the toggle switch with, SHUTDOWN, OPERATE, and STANDBY positions. Of course, you may still operate the Laser System remotely by extending Pins 1 & 5 and 2 & 6, of D. lfthe remote operation is used, then the Toggle (or the rotary) switch is put in the RUN or OPERATE position, and control is by the remote box. 26
  • SECTION 3.0 GUIDE TO TROUBLE SHOOTING AND FOR OMNICHROME As shipped from the factory, your Omnichrome helium-cadmium laser should provide peak performance with no adjuslment or alignment. Should there occur any problem during the life orihe laser system, the following guide should be of help in identifying the problem and its solution. Before beginning a potentially lengthy trouble shooting procedure: I. Is there A.C. to laser system?2. Is there any blockage or restriction of cooling air flow to the laser head or power supply?3. Is the red power supply overtelTlperature lockout status light "on"?4. Is there anything blocking the laser beam?5. Did you wait 5-10 minutes from initial turn-on?6. Is the laser status light on in the head?7. Are the cables firmly mated at the rear of the power supply?8. Is the red overcurrent status light "on"?9. Is emergency keyswitch "on" (horizontal position)? lfnot, turn keyswitch "on".Three categories of trouble shooting are described below:1. Laser system will not start, no laser output or system shuts off.2. Low laser output power.3. Laser output power fluctuates.Note: THE KEY SWITCH ON THE FRONT PANEL OF THE POWER SUPPLY ISNOT TO BE USED FOR NORMAL SHUTDOWN OF THE LASER. THIS KEYSWITCH IS FOR EMERGENCY TURN-OFF ONLY. USE THE ROTARY SWITCHFOR NORMAL OPERATION OF THE LASER. 27
  • SUMMARY OF HE-CD LASER MALFUNCTION INDICATORSINDICATOR NORMAL CONDlTIONPOWER SUPPLY INDICATORSGREEN "POWER ON" STATUS LIGHT (FRONT PANEL) ON -"ON" INDICATES AC POWER TO POWER SUPPL Y. -"OFF" INDICATES NOT AC POWER TO POWER SUPPLY. - CHECK AC LINE OR MAIN PIS FUSE.YELLOW "Cd HEATER" STATUS LIGHT (FRONT PANEL) ON - "ON" INDICATES CD HEATER ON AND DISCHARGE ON. - "OFF" INDICATES NO DISCHARGE OR CD HEATER CIRCUIT MALFUNCTION (SEE SECTION 2.2.2).YELLOW "He HEATER" STATUS LIGHT (FRONT PANEL) ON OR OFF - "ON" INDICATES TUBE ASKING FOR HELIUM. - NORMALLY "ON" FOR 1ST 5 TO 15 MINUTES OF OPERATION. - NORMALLY "OFF" DURING LONG TERM OPERATION. - IF "ON" FOR MANY HOURS SEE SECTION 2.2.3.RED "TEMP LOCKOUT" STATUS LIGHT (FRONT PANEL) OFF - "ON" INDICATES PLASMA TUBE IS TOO HOT TO START. - IF "ON" LEAVE LASER OPERATING. IT WILL COOL DOWN AND RESTART. - TYPICALL Y CAUSED BY AC LINE INTERRUPTION OR NO COOLING. - SEE SECTION 2.2.7RED "OVERCURRENT LOCKOUT" STATUS LIGHT (CAN BE SEEN OFF INSIDE PIS THRU AIR INLET LOUVRES). - "ON" INDICATES TUBE CURRENT TOO HIGH. IF "ON", UNPLUG AC LINE TO PIS, WAIT 3 SEC AND RESTART. - SEE SECTION 2.2.8POWER SUPPLY COOLING FAN (REAR PANEL) ON - "OFF" INDICATES OVERTEMP LOCKOUT CONDlTION OR HIGH VOLTAGE CIRCUIT FAILURE IN PIS. - SEE SECTION 2.2.1.LASER HEAD INDICATORSRED INDICATOR LIGHT (FRONT PANEL) ON - "ON" INDICATES AIC POWER TO LASER IIEADLASER PLASMA TUBE DISCHARGE (INSIDE HEAD) ON - "ON" INDICATES ll1GlI VOLTAGE CIRCUIT FUNCTIONS -IF "OFF", ClIECK IF "OVERTEMP LOCKOUT" STATUS LIGHT IS "ON", OR HIGH VOLTAGE CIRCUIT HAS MALFUNCTIONED - SEE SECTION 2.2.1.LASER HEAD FAN ON - "ON" INDICATES LOW VOLTAGE CIRCUIT ENERGIZED. -IF "OFF", PIS LOW VOLTAGE SECTION MALFUNCTION. 28
  • LASER HEAD TEST POINT MEASUREMENTS USE A HIGH IlviPEDANCE, NON GROUNDED, DIGITAL VOLTMETERTEST POINTS------------------------------------------------------ -~----------------------------------------------BLACK TO BLUE 1.O±.05 - MEASUIU~S PLASMA TUBE DISCHARGE CURRENT (1 VDC=l OOmA) - SHOULD BE STEADY WITHIN 10mV.BLACK TO RED -FOR 39X, 1.2±.1 VDC -FOR 56X, 1.8±. J VDC -FOR 74X, 2.6±.lVDC -FOR 112X,1.8±.lVDC - MEASUIUiS PLASMA TUBE VOLTAGE (1 lOOnV) - VOLTAGE SHOULD BE STEADY WITHIN lOmV,MAX. - IF LARGE VARIATIONS (>30mV) OCCUR WITH PERJOD IN RANGE OF 30 SECONDS, CHANGE TUBE VOLTAGE UPWARD USING "Vt ADJ" POT ON LOWER REAR OF LASER HEAD.BLACK TO YELLOW 9.S±.7VDC - MEASURES HELIUM PRESSURE REGULATION SET POINT. - SHOULD BE STEADY WITHIN LESS THAN lOmV. - THIS VOLTAGE IS FACTORY ADJUSTED ONLY USING THE "VR ADJ" POTENTIOMETER ON LOWER REAR OF LASER HEAD. 29
  • CAUTIONDO NOT ATTEMPT TO MAKE ANY ELECTRONIC MEASUREMENTS WITHOUTREADING THE FOLLOWING:1. There are potentially lethal voltages inside the power supply laser head. Exercise extreme caution if covers are removed.2. Before starting laser to perform fault diagnosis - install a line isolation transformer since circuits are at line potential. Component failures can otherwise occur during probe testing.3. If an oscilloscope is to be used - isolate the oscilloscope from the line and ensure that personnel do not touch scope cabinet during test.4. The highest voltages accessible inside the Power Supply arc at the terminals of the two parallel 10K ceramic resistors located in front orthe exhaust f~m.5. Only a limited number oftest points can be probed during operating ofthe PIS without damaging components. Low Voltage circuits should be tested only aiter removing push-on terminals to "high voltage" bridge rectifier adjacent to large filter capacitor. Be certain that those push-on terminals dont touch the chassis or any other paxis during testing since 115 V power is present. REFER TO DIAGNOSTIC FLOW CHART LASER WILL NOT NO LASER OUTPUT LASER SHUTS OFF3.1 When the laser system is turned "on", did the laser plasma tuhe discharge light? i.e. [s there a neon-sign-type sidelight emanating from the side of the glass laser tube when viewed from the laser head air inlet or exhaust apertures. 3.1.1. If tube discharge is "off" 1, go to Paragraph 2.0 3.1.2 If tube discharge is "on", 1 go to Paragraph 6.0 30
  • UNIT WILL NOT START NO LASER OUTPUT LASER SHUTS OFF lAM) TU& OISOIAFGE IS I I I IIC STATUS LIGHT IS j I CD HEA1&R llGHT IS j OFF 00 OFF I ON I 1. QiEO( PIC PWR TO PWR SUPPLY I I OVERTEMP Loo<.OU II 1. Q1E0( I REM01& CONTROl FOR I 1. Q1E0( lASE R BENoi :2. QiEO( IoIAIN PWR SUPFL Y FUSE LIGHT IS STAIa3Y MODE. FOR ElLoc::KAGE. UK niX CM-I I D1fOJ1E PHOf£ OR 1VX (JoINIOflDE 2. VIEW DlSOlAFGE I Pi"IUit: FOR INSTRUCTIONS. FOR INSTRUCTIONS. lHFIOI.JGH AI R INI..ET! OFF 00 OR OUTLET. OBSERVE DlSD1ARGE COLORw I I 1 • ALLOII SYSTEM TO RUN CP.lN< OR BUIE) PHOf£ OR 1& LEX OVERCURRENT Loc::KOUT LIGHT IS I (WAlT 10-15 MIN.) CMi I OIfOJ1E j OFF I 00 PHOt£ OR TELEX I POI/ER SUPfLY COOLlI«> FAN 1 UNPLUG Ale CORD FROM WALL. WAlT ::I SECOH)S. OMNIOIRCME • PLUG BAa< IN. OFF I ON PHOt£ OR TELEX ::.MI I OIRCME • Note: When contecting Omnichrome. r stage of this flow chart. t PHOt£ OR TELfX I 1. OlEO( HEAD CABLE CONr-ECTOR l (JoIN IOIRCME J (STRAIGHTEN &NT PINS) PHOt£ OR TELEX OMNIOlRCME FOR INSTRUCTIONS.
  • 3.2. Check status ofthe green power supply Power-On status light for "on" or "off. 3.2.1. If the Power-On status light is "off, continue. 3.2.1.1 Check AlC power to power supply - wall outlet, AIC cable and connector; must be 104 to 128 Volts, Low Voltage will not energize K 1, WB4. 3.2.1.2. Check remote control circuits and interlocks. 3.2.1.3. Check main fuse if Power Supply on back panel. 3.2.1.4. Check Klan WB4 and associated AIC control circuits. 3.2.2. lfthe AIC status light is "on", and keyswitch is "on" (horizontal position), go to Paragraph 3.0; otherwise turn keyswitch "on" .3.3. Check status of the red power supply TEMP LOCKOUT light for "on" or "ofT. 3.3.1. If the TEMP LOCKOUT light is "off, go to Paragraph 4.0. 3.3.2. If the TEMP LOCKOUT light is "on", continue. 3.3.2.2. Check fan on laser head for correct operation. Check AIC connector on fan . Fan should show a modest but steady flow of air in the range of IOta 20 CFM. 3.2.2.3. Does the ambient temperature exceed 100 F (38 C)? Excessive ambient temperature can cause plasma tube overtemperature circuit to activate. 3.3.2.4. Wait for IOta 15 minutes with laser system turned on. AIC power interruption will cause TEMP LOCKOUT which will recover most rapidly with system (and head fan) turned on. System will re-start and re-regulate automatically.3.4. Check status of fan in laser head for "on" or "ofT. 3.4.1. If head fan is "off" this indicates a malfunction in the low voltage circuit in the power supply. Check circuit associated with K2 on back panel of PIS and U2 ofWBl. 32
  • 3.4.2. If head fan is "on", go to Paragraph 5.3.5. Check status of fan in power supply. 3.5.1. If PIS fan is "off, continue. 3.5.1.0. Check to see ifOVERCURRENT light is "on". (Visible through louvers PIS cover). If OVERCURRENT light is "on", unplug AC cable, wait 3 seconds and plug back in. If OVERCURRENT light comes "on" again, then an overcurrent condition exists. Check 1 amp fuse (F8; with connectors to left, it is the last fuse to the right, next to blank position). any rate, a blown tuse results in an overcurrent condition. Overcurrent can also be caused by a faulty or "weak" Q9 optocollplcr. And, finally, a shorted Q2, MJ 10007 Transistor. 3.5.1.1. Check low and high voltage connectors at rear of power supply. IfH.V. Connector has an internal arc- over, overcurrent light will come "on". If so repotting is required. Interlock circuit in each connector will inhibit high voltage circuit and PIS ran. Look for bent, pushed back or arc damaged pins and repair. Make sure BV plug has all ic)Ur red "0" rings and is tightly mated to receptacle in PIS. Sec that keyswitch is "on" (horizontal position). 3.5.1.2. Check for correct laser head/power supply combination. Series 39X, 56X, and 112X laser heads can be used with any Modell 00 or Model lOOA power supply. Series 74X laser heads can be used only with a Modell OOB power supply. 3.5.1.3. Check for failed components or fuses in the PIS. If fuses are blown this indicates one or more failed components in PIS. Fuses in circuit are to limit damage due to failure toreplacement components. Identity of blown fuses will approximately indicate failed components. If main fuse is blown, there is probably a major fault or short in the power supply. If transistor base fuses on Q2, Q3, and Q4 are blown, 33
  • replace standard package of parts including: All three power transistors (Q2, Q3 & Q4), two 2N2222s, the 6N 136, the SG3627, and the SN7474. 3.5.2. If PIS fan is "on", continue. 3.5.2.1. Check PIS function using an alternate laser head if available. 3.5.2.2. Observe laser head and PIS for sound and/or visual indications or arcing or smoking. 3.5.2.3. Check BV connector for bent, pushed back or arc damaged pins. Repair and remate firmly . 3.5.2.4. Check Plasma Tube Voltage between outside terminal of ballast resistors (R7i and R8) and chassis ground (39~ 1,3K v, 56 ~2K v, these are cold tube voltages). 3.5.2.5. - Check Plasma Tube filament cold resistance, should be 0.9 + 0.1 Ohm from ~ to Pin 12 on low voltage laser head connector (P 1). If open circuit, change Plasma Tube connection to alternate filament. Inside laser head cover adjacent to output end of plasma tube. Common terminal for "Normal" and "Spare" Cathode is marked with Black. Open filament may indicate plasma tube is "up to air", IE, has cracked glassware. 3.5.2.6. Remove and inspect Plasma Tube for cracks or leaks, see separate procedure. 3.5 .2.7 Install a new Plasma Tube per separate procedure.3.6. Check status of yellow power supply Cd HTR light for "on" or "011". 3.6.1. If Cd HTR is off, continue. 3.6.1.1. Check remote control circuit to ensure unit is not in standby mode and that external standby circuit is properly implemented. 34
  • 3.6.1.2. Is Cd HTR light blinking? Observe light for 2 to 3 minute period to note changes and regularity of light intensity level and ensure that light is truly ofI. 3.6.1.3. Check Cd triac (Q 1 on associated circuitry. (See Section 2.2.2 and 5.15). 3.6.1.4. Check continuity of heater circuit in laser head. Heater resistance should be 1.75 + 0.2 OHM 1rom Pin 8 to 10 of PI (Low voltage head cable, 16pin). 3.6.1.5. Check 10M OHM tube voltage sampling resistor fiom PI, 4 to P2, 4 (High voltage 4 pin cable). 3.6.2. If Cd HTR light is "on", continue. 3.6.2.1. Check optical system for beam blockage. 3.6.2.2. Check Plasma Tube sidelight color by observing through head fan aperture or air inlet aperture. A pink sidelight color is normal. Blue sidelight color indicates shorted or other problem with triac control circuit (Q 1 on WB2). Check triac and associated circuitry and 10M resistor in HV cable. 3.6.2.3. Is Cd HTR light blinking? Observe light for 2 to 3 minutes to note changes and regularity of light intensity level. 3.6.2.4. For Series 39X remove top cover and manually deform the (cathode) mirror flange all to see if output beam can be achieved. DO NOT TOUCH ANODE MIRROR FLANGE AT AIR EXHAUST END OF LASER I-lEAD. LETHAL HIGH VOLTAGES ARE PRESENT. For Series 56X and 112X laser heads, see later section on resonator alignment.3.7. Laser Output Power is low. In order of increasing difficulty, perform the following: 35
  • 3.7.1. Check records on laser system. Is the laser output low compared to a previous measurement using the same radiometer and measurement technique?3.7.2. Review measurement equipment and technique. Is the radiometer calibration current? Is the beam diameter too large or small at the detector surface for an accurate measurement? small beam can cause overload of detector.3.7.3. Check for dirty or obstructed optical elements between the laser and radiometer.3.7.4. Check for low NC line voltage. The line voltage should nominally be greater than 104 VAC.3.7.5. Check the Jaser head cooling air now for blockage either at air inlet or outlet.3.7.SA. Check for loose plasma tube in laser head by gently shaking. Ifloose perform procedures described later in Section 4.3.7.6. Check ambient temperature. Normal range is between 50 F and 100 F (10 C to 40 C). Ambient temperature range is exceeded when Cd BTR duty cycle reaches its limits of 20% (ambient too high) or 80% (ambient too low).3.7.7. Check plasma tube discharge current (J 00 mA nominal). Read voltage between black and blue test points on the back panel ofthe laser head. Use a non-grounded digital multi meter . Measurement should be 1.0+/- 0.02 V (lVIlOOmA). Usual fault condition is Q9 failure causing greater than 1.2V (or l20mA). Overcurrent LED inside power supply will come on if tube current exceeds 112mA.3.7.8. Check plasma tube operating voltage to ensure operation within normal range. Measure this voltage between the black and red test points on the back panel of the laser head. Series 39X laser heads should read about .9SVDC. Series S6X heads should read about 1.6VDC. If voltage is outside of this range, check either the triac control circuit (Q 1 or WB2), or the plasma tube reference voltage circuit (Terminal 9 of WB3 and associated reference resistors R19 of WB3 and 10M reference resistor in the head cable between terminalS ofWB3 and Pin 4 ofP2). 36
  • 3.7.9. Adjust cadmium pressure adjustment potentiometer R2 on WB3 (accessible on rear panel of all 39X and 56X laser heads and on the side of 112X laser heads. Pots are labeled Vt ADJ. Clockwise produces increased plasma tube voltage which relates to decreased cadmium pressure. Counterclockwise produces decreased tube voltage (increased cadmium pressure). WAIT. CIRCUIT IS SLOW AND CAN TAKE 30- 60 SECONDS TO RESPOND. Note if laser output can increasedI, with this adjustment. 3.7.10. Check plasma tube resonator alignment. See Section 4.0. 3.7.11. If none ofthe above procedures is adequate to bring the laser output power up to an acceptable level, internal damage within the laser plasma tube may be excessive. If this occurs within the warranty period, return the laser head to Omnichrome where the plasma tube will be replaced at no charge. 3.8. Laser output power fluctuates or optical noise is excessive. In order of increasing difficulty, perform the following: 3.8.1. Monitor laser output and note frequency of output power fluctuation. Very low frequency power output fluctuations in the order of 2 to 10 cycles per minute indicate instability in the cadmium pressure control circuit. Moderate frequency fluctuations in the 10Hz to 50 frequency range are due to random plasma noise in the plasma tube. High frequency fluctuations in the 250 KHz to 350 KHz range are due to a plasma wave resonance in the plasma tube. 3.8.2. lfthe laser output fluctuations are very low frequency 2-10 CPM this can usually eliminated by one of two procedures. 3.8.2.1. Change the plasma tube voltage by + 10-20 volts using Vt ADJ pot and monitoring voltage at the Vt test point on the rear panel of the laser head. Note that test points measure IV per 1000V of tube voltage. Wait 10-15 minutes between each voltage change to see if output stabilizes. If this procedure fails, continue. 3.8.2.2. Put laser in standby mode for 10-20 hours, then return to normal operation and monitor output stability. Repeat this procedure, if necessary. 37
  • 3.8.3. Iflaser output fluctuations are excessive in the moderate to high frequency range (10 Hz to 350 KHz), this can normally be corrected by adjusting cadmium vapor pressure (tube voltage). Low optical noise generally occurs in a narrow range of tube voltage, so perform adjustment carefully. 3.8.4. If none of the above procedures is adequate, there may be a fault with the helium pressure regulator which caused excessive helium pressure within the plasma tube, or cathode damage has occurred. Change cathode connectors on the plasma tube from the normal to 5pare cathode. The common terminal for the normal and spare cathode is marked with black.3.9. Laser beam is distorted The output beam from the laser exhibils excessive scatter or the beam pattern is not uniform, the likely cause is contamination of the output laser mirror, by dust, oil vapor or other foreign materials. Cleaning of the output mirror is best done with acetone although alcohol is sometimes adequate. 3.9.1. Series 39X, 56X, and 74X optics cleaning: Open the output aperture slide on the front of the laser head. Clean exposed output mirror surface with "Q" tip or optical tissue and acetone. 3.9.2. Series 112 Optics cleaning: Warning: The series 112 laser mirrors are glass-to-metal sealed into an anode assembly on each end ofthe laser. This metal flange which can be seen as an annulus around the laser mirror is operated near 2000 VOLTS. CLEAN OPTICS ONLY WITH OPTICAL TISSUES OR Q-TIPS USING ACETONE OR ALCOHOL AND ONLY USING A DIELECTRIC TISSUE HOLDER. A Q- Tip is adequate for output laser mirror cleaning. If laser output is only about 20 mW at 442 nm, check to see ifboth power supplies are turned on. If both are on, check to see if both discharge capillaries are lit by observing thru cooling fan. 38
  • Items 5.2.1,1, and 3 above can quickly be ascertained to a moreextensive field or factory evaluation. If any problems occurbeyond those described above, contact your nearest Omnichromerepresentative for instructions. 39
  • 40
  • SECTION 4.0 LASER HEAD TEST, ALIGNIAENT & ADJUSTMENT4.1 STATIC CONTINUITY TESTS Every laser head has a 16 pin low voltage cable terminated by connector PI and a 4 pin high voltage cable terminated by connector P2. Inspect these connectors for burned or pushed-back pins. Then perform the static continuity and resistance measurements on a disconnected laser head using a high impedance ohmeter as described in Table 1.These measurements will not ensure proper operation of a laser head but will ensure thatno malfunction within the laser head can cause damage to a power supply. pi TADlEI Pl o lASER HEAD CONNECTOR CONTINUITY AND RESISTANCE VALUES MEASUREMENT POINTSITEM FROM TO OHMS COMMENTI. 11 , 1 11,4 Diode Test (Forward Conduction)2. 11,2 11,4 3 to 5 K3. 11 ,6 PI,4 20-21K FOR 39X 12-I3K FOR 56X 10K FOR 74X II-12K FOR 112X4. PI,S PI,4 5K5. 11,8 1,9 2.8 HELIUM RESER VOIR HEATER6. 11 ,8 11 , 10 1.8 CAO RESERVOIR HEATER7. 11,11 11,12 0.9 CA THODE FILAMENTB. PI,I3 PI,14 OJ9. PI , I 5 PI,16 325 HEAD FAN COIL10. 11,3 PI,4 OlON 200 IS VTOGNOII. 11,7 PI ,4 OLON 200 CASE TO CKT GNO12. 11 ,8 11,4 OL ON 200 IITRS TOGNO13. 11,11 11,4 01. ON 200 IlL TOGNO 14 . 11,15 11,4 OL ON 200 FAN TO GND15 . 11,16 11,4 OLON 200 FAN TOGNO16. 11,13 11,4 OLON 200 INTERLOCK TO GNO17. *-h,I .w. <.3 OLON 20018 .19.20. ~ P24 :in: ..W- OLON 200 OLON 200 11,4 IOMEG±5%21.22. !I PI,4 OLON 200P I is the 16 pin low voltage connector. P2 is 4 pin HV connector. 41
  • 4.2 RESONATOR ALIGNMENT Omnichrome He-Cd lasers have three resonator types. The Series 39X lasers utilize the plasma tube itself to maintain alignment of the laser mirrors, similar to state-of-the-art He-Ne lasers. Series 56X lasers use a 24 annealed Invar welded structure. Series 112X lasers use a 48" annealed lnvar welded structure. The procedure for the alignment of each type of resonator differ substantially. If the laser output is zero or low and resonator alignment is suspected, first check to ensure that: 1. Sufficient time has elapsed for the plasma tube to warm up. 2. No electronics problem exists such as tube anode voltage regulation. 3. Turn off the laser and remove safety key. Shine a nashlight into the helium regulator assembly. Look into the output laser mirror and down the discharge capillary to see if condensed cadmium in the condenser section of the plasma tube has built up enough to internally block the laser beam. If so, remove the blockage using the condenser remelt timer on the back panel of the head. 4. Inspect laser mirrors for internal deposits or films which are visible from scattered light from the discharge. If so, remove films using procedure in Section 4.3. If the plasma tube appears to operating normally continue. 4.2.1. Series 39X Resonator Alignment Series 39X laser resonators are integral with the glass tubes and use adjustable flanges on the ends of the plasma tube for mirror ali gnment. Remove the front panel of the laser head by removing the screws which hold the panel on the bottom of the laser head and the screws on each side. If the laser output is lower than expected, manually deform the output mirror flange all directions while monitoring laser output by axially pushing with a finger around the edge of the 1.75 inch diameter mirror flange. If one position causes laser power to increase, adjust the appropriate set screw to maximize laser output. If laser power is not adequately recovered by this process, check to see if the beam is centered in the output laser mirror. If not, anode mirror adjustment may 42
  • be necessary. DANGER: THE ANODE LASER MIRROR OPERA TES A T VOLTAGES OVER 1000 VOLTS. EXTREME CARE MUST BE EXERCISED WHEN ADJUSTING To adjust anode laser mitTor first remove the remote cooling cover plate on the back end of the laser head. Do not leave cover plate off for a long period of time since this will cause overheating of the plasma tube. adjust laser mirror use a 1116 inch Allen wrench with well insulated handle and shank. After removing cover plate, adjust laser mirror in direction to cause laser beam to center in output mirror. This will cause output to drop until the output mirror is readjusted for maximum output. This process is repeated until best output of the plasma tube is achieved. If the output remains low, recheck the introductory items of Section 4.2. If no laser output occurs the procedure may require the use of an autocollimator. Before this, perform the simple check of manually deforming the output mirror flange to see if laser output can be produced. DANGER HIGH VOLTAGE. If so, continue optimization process described above. If not, refer to procedures in Section 4.3.4.2.2. Series 56X Resonator Alignment Series 56X laser resonators are annealed lnvar welded structures. The plasma tube is suspended in the invar resonator, held only at the mirror flange ends which allow [or mirror alignment. All adjustment of the resonator is performed using any of six nuts on each end of the three invar rods. Remove the front panel of the laser head by removing the appropriate screws on sides and bottom of the laser Also remove remote cooling cover plate on the back paneL Inside you will see three nuts (3/8 inch) on each end of the laser resonator. For each ofthese six visible nuts on the front and back of the laser, there is a mating back up nut not visible on the inside. If the laser output is lower than expected, manually deform the resonator by pushing inward along the rod axis on each of the sixnuts. If one location causes output to increase, adjust the appropriate nut to achieve maximum output. "Walk" the resonator at anode and cathode ends until maximum output is achieved. 43
  • If the resonator is badly out of alignment, it may be necessary to remove the laser head housing to provide better access for alignment. 1. Tum laser" off . 2. Remove top cover of laser head by removing screws on sides of the laser head. 3. Remove the bottom cover by removing six nuts inside laser head which hold resonator base plate in bottom cover. 4. Remove base plate assembly with back panel and plasma tube/resonator assembly attached. 5. Tum laser "on" and repeat previous resonator alignment procedures. If no laser output occurs the procedure may require the use of an autocollimator. Before this, perform the simple check of manually deforming resonator to see if laser output can be produced. If so, continue optimization process described above. If not, refer to Section 4.3.4.2.3. Series 112X Resonator Alignment Series 112X laser resonators are annealled lnvar welded structures. The plasma tube is suspended in the invar resonator, held at each end and also supported radially in the center. All adj ustmcnt of the resonator is performed using any of the six nuts on each end of the resonator and three radial set screws at the center of the resonator. The purpose of the center set screws is to align the two separate sections of the laser discharge capillary. The purpose of the 12 nuts on the ends of the resonator is to align the laser mirrors with respect to the discharge capillary and each other. Remove the end covers from both ends of the laser head (3 screws on each end). Exposed on each end ofthe laser head will be a 112 inch thick ceramic plate to which the laser mirrors are mounted. These plates are supported by three Invar rods clamped by six nuts. If the laser output is lower than expected, manually deform the resonator by pushing inward along the rod axis on each of the sixrods. If one location causes output to increase, adjust the appropriate nut to achieve maximum output. On Series 112 laser heads it is also necessary to adjust the "center" of the laser. At the laser center the plasma tube is supported by a set screw located directly under the hub of the cooling 44
  • fan. Two additional set screws are located 120 in either direction around the head housing from the fan centerline. The screws located at 120 can be accessed through holes in the housing. CAUTION: Use a 3/32 Allen wrench insulated with heat except for the tip for adjusting the 120 set screws. No high voltage is present near these adjustment screws although access is through a low voltage printed circuit board and contact can cause the plasma tube to extinguish. Adjust these three "center" screws for maximum output.r If no laser output occurs the procedure may require the use of an autocollimator. Before this, perform the simple check of manually deforming the resonator to see if laser output can be produced. so, continue the optimization process described above. not, refer to Section 4.3. 4.3 PROCEDURES FOR NO LASER OUTPUT This section describes procedures to be used if no laser output occurs and all electronics have been checked to be working properly. No laser output can only result from one or more of four factors: Resonator mirror misalignment, mirror damage, condenser blockage, or cadmium reservoir depletion. If the plasma tube has been operated less than about 4000 hours cadmium reservoir depletion is an unlikely occurrence. Before attempting major realignment of the resonator mirrors check for damage or condenser blockage. With the plasma tube "on" examine the output and rear mirror for films or particulate material on the surface. Films or particulate material usually deposit in a circular pattern centered on the laser mirror and are visible as a fog or high light scatter area dissimilar from the remainder of the laser mirror. These films can usually be removed using a 500 Watt heat gun, but this procedure is performed with the plasma tube removed from the resonator. 45
  • 46
  • SECTION 5 POWER SUPPLY TEST AND ADJUSTMENT REVISIOND5.1. PROCEDURE ESTABLISHES THE STEP BY INSTRUCTIONS ELECTRlCAL CHECKOUT OF THE SUPPLY, REVISION5.2. EQUIPMENT 5.2.1. Multimeter with clip-on test leads. 5.2.2. H.V. test meter with 0-2V & 0-2KV ranges, with test leads. 5.2.3. Oscilloscope with lOX probes. 5.2.4. Resistive Load Box for preliminary checkout. 5.2.5. 8 Amp Variac and 500 Watt isolation transformer (before variac).5.3. PRE-TEST 5.3.1. Blowout the entire chassis with compressed air; look for any bits of wire or solder left in the supply. 5.3.2. Inspect for loose or missing hardware. Replace or tighten any found. 5.3.3. Bend the 50 Watt, 10K resistors up into the air flow and see that none of the wiring is touching the resistors. 5.3 Insert the required I.e.s in their respective 0UVJl-hl use tested optocouplers: 5.3.4.1. Q4, 9, 26 = 50 to 1.00 Gain (4N25) 5.3.4.2. Q24 = .25 to .65 Gain (6N136) (add resistor between pins 5 & 7 to adjust gain: clip off pin 7 before installing I.e.) 5.3.4.3. Insert fuses: F1 = 8.0ASB F2,3,4 = 3/8A F5,8 = 1.OA F6,7,9 =8.0A 47
  • 5.3.4.4. Insert MJI 0007s with thermal compund and attach to heat sinks with #6 x 5/8 sheet metal screws. 5.3.4.5. For model 100 or 156, install following Q23 = 2N2222 Q22 = 2N3020 U4 = 7474N U6 = 3627J5.4. AC LINE CHECK 5.4.1. Continuity: 13, 7 to FI, 1 FI, 1 to K2, 1 FI, 1 to Kl, 1 FI, 1 to rotary Switch, SIA, Wiper FI, 1 to PWB4-1, 1 5.4.2. Switched AC Checks: Kl, 2 to FANI (org) & CRt, (I-IV. Bridge) K2, 2 to Ti, 2 K2, 4 to ,1 5.4.3. Resistance Checks: Cl(+) to Cl(-) + 10 Ohms C19(+) to C19(-) = "aL" C5(+) to C5(-) = "OL" C8(+) to C8(-) = 3.56K+/-.25K(20K scale) C9(+) to C9(-) = <.3 Ohm C4(+) to C4(-) = "aL" C3(+) to C3(-) = 190 to 225 Ohms (2K scale)5.5 AC CHECKOUT 5.5.1. Disconnect spade terminals from CRl, H.V. Bridge. 5.5.2. Hook-up, AC, L.V., & H.V. connectors (from resistive load box) & use adaptor if testing a Model 156 supply. 5.5.3. Tum rotaryswitch to "Shutdown" position & plug AC cord into Variac (KEY "ON"). 48
  • 5.5 With Variac at "0", turn Variac "ON". 5.5.5. Connect Multi-meter (20V scale) across the 100u, 16 or 25V on PWB4-1 note voltage as Variac is 5.5.6. With Variac at "10", meter should read approx. 1.8v. Ifnot, turn down Variac & recheck connections. 5.5.7. Record voltage reading when relay actuates (K3, <8v). 5.5.8. Record voltage reading when relay drops-out (> l.5v). 5.5.9. With Variac at "100", turn "ON" "OFF" 10 a out or "plug-pull". 5.5.9.1. Note 1/2 sec delay in K3, when turned "ON", & immediate response when turned "OFF". 5 .6. CONTINUITY CHECK, K3 RELAY 5.6.1. Multimeter across Cl. (200 Ohm scale) 5.6.1.1. Relay "OFF" = 10 Ohms 5.6.1.2. Relay "ON" = "OL It 5.6.2. Meter across C9. 5.6.2.1. Relay "OFF" = <.3 Ohm 5.6.2.2. Relay "ON" = "OL" 5.7. LOW VOLTAGE CHECKOUT 5.7.1. Turn "OFF" Variac (rotary switch, "SHUTDOWN", and AC cord still0f connected to Variac). 5.7.2. With Variac at "100", turn "ON" Variac, then turn the Rotaryswitch to "OPERATE". 5.7.2.1. Green "Power" Light should be bright and steady. 49
  • 5.7.2.2. If the Fan in power supply comes "ON", continue test. If not, tum "OFF" Variac IMMEDIATELY, and check for faulty components or solder bridges on WB 1. Also, look folded-over "legs" on LC.s. 5.7.2.3. Check U3, 5V regulator, for clearance of sink to circuit board. Should be <1132". Lower U3 by heating all three legs at once. After lowering, add a little fresh solder 10 each connection. Check [or no solder bridges. 5.7.3. With Muitimeter, measure the following: C 19 = 17 to 21 v (check polarity of capacitors). C5 = IS to 20v C8 = 5 +1-.lSv C3 = 9 to 13v C4 = 9 to 13v 5.7.4. If all voltages check out, continue test.5.8. FILAMENT VOLTAGE CALIBRATION 5.8.1. Connect Meter (20v scale), (-) to PWB 1, 19. 5.8.1.l. Adjust R2, on PWBl, to obtain 5.55v. 5.8.1.2. See that all three I.c.s, on WB2, are tight against chassis with thermal compound of both sides of mica washers. Use 2-56X1I4 screw with shoulder-washer & nut to secure the I.C.s firmly to the chassis.5.9. SWITCHING TIME CALIBRATION 5.9.1. Using floating scope ground, connect probe ground to PWBl,9 and probe tip to top side ofRl18 (lOv/div, Su Sec/div, source: ChI) (be certain the V AR knob is clockwise to stop). 5.9.2. The resulting waveform should have a period of24 to 2S uSee. (must not exceed 25 uSec). See scope photo # 1. 5.9.3. The period may be adjusted by RIll on PWBl. 50
  • 5.10. CHECKING INVERTER DRIVE 5.10.1. Using same probe ground (PWBl,9) place probe on F3, then F4 (left side of fuses) (2v/div, 10 uSec/div). 5.10.2. The waveforms should look like scope photo #2, and have a (+) peak over l.5v, but <2.0v. 5.10.3. If peak level falls below 1.5v or over 2.0, Q3 or Q4 may be faulty.5.] 1 CHECKING SWITCHER DRIVE 5.11.1. Connect scope probe ground wire to PWBl, 13, touch probe tip to right side of F2; waveforms should look like scope photo #3.5.12. FULL POWER CHECK 5.12.1. Disconnect power cord from Variac, turn "OFF" Variac and reduce to "0". 5.12.2. Connect power cord, with rotaryswitch in "SHUTDOWN", to AC Line outlet (no isolation). 5.12.3. Connect "cheater" cord to H.V. Bridge and plug into Variac. 5.12.4. Connect 2KV meier to chassis ground and outside end of 10K, SOW resistors (+). 5.12.5. Connect 20v lead to (-) end ofC19. 5.12.6. Connect scope probe ground wire to PWB 1, 9 and probe tip to post #2 on Chassis (SOv/div, 10 uSee/div, set trace to next to bottom graticule line). 5.12.7. Turn rotaryswitch to "OPERATE". Supply fan will come on. 5.12.8. Turn "ON" Variac and slowly increase, watching scope trace and voltmeter (20v scale). See scope photo #4. If any oscillations or instabilities occur, QUICKLY turn down the Variac. Otherwise, continue. 51
  • 5.12.9. At "80" on Variac, the voltmeter should read LOOv +/- .02v, (l00=/-2rnA) and the scope trace should be about 280v and peaked out, for a Model 139; at "60" on Variac, <250v, for a Model 100 or 156. 5.12.9.1. Any further increase in Variac setting should not the scope display or the voltage across R48 as displayed by the voltmeter. the voltage continues to rise and reaches 1.10v, turn down the Variac to "0". Ifthe reading is <.98v or >1.02v but <l.lOv, then trim by adding resistors at R42 or R43 until the reading is in tolerance (use decade box to determine value). 5.12.9.2. Ifthe voltage remains at 1.00v+/-.02v, then increase Variac to "1 00" (full 115V line setting). 5.12.9.3. Record voltmeter reading, then turn "OFF" rotaryswitch momentarily. The reading should be .83v+/-.03v. Record reading. DO NOT LEAVE ROTARYSWITCH "OFF" FOR MORE THAN ONE MINUTE, while Variac is connected to CRl, Bridge. 5.12.9.4. If operation checks out, then "snap" Variac "OFF", noting that voltmeter goes to "0". Then, "snap" Variac back "ON" and note that the voltmeter returns to the original reading. 5.12.9.5. Turn "OFF" Variac and unplug "cheater" cord from Variac. Turn down Variac to "0".5.12.10. Thermal Lockout Trip Points 5.12.10.1. Unplug AC cord from supply. Remove scope probe. 5.12.10.2. Disconnect "cheater" cord from H.V. Bridge. Reconnect spade lugs to H.V. Bridge. 5.12.10.3. Connect multimeter, (-) to negative end ofC19; (+) to bottom of R76. 5.12.10.4. ReconnectAC cord. Turn "ON" rotaryswitch. 5.12.10.5. Tube current should be lOO+/-2mA. Read multimeter on 2V scale and record reading at "R " on checkout sheet (should be .25v+/-.003v). 52
  • 5.12.10.6. Tum Keyswitch "OFF" and record meter reading at "S: "on checkout sheet (should be .51-.54v). Turn Keyswitch back "ON" and check: "KEYS WITCH _ _ _ _" on checkout sheet. Remove AC supply. 5.12.11. Overcurrent Check 5.12.11.1. Connect decade box to R39 (both sides) with box set at 29000 Ohms. 5.12.l1.2. ReconnectAC cord to supply. Tube current should be approx. 108 rnA (1.08v). Slowly reduce the box resistance, 1K at a time, until tube goes out and red LED on the Overcurrent board lights. Record highest tube current observed, at: "O.c. mA" on checkout sheet. Should be J 14 to 116 mAo If not, change value of 68 Ohm resistor on WB4-1 board; higher value = lower current, and lower value = higher current. 5.12.12. He Hir Check 5.12.12.1. Tum "ON" He Htr switch, located on Load Box. Both, Load Box He Htr LED and power supply lIe Htr LEDs must light. Check step # 14 on checkout sheet this is so.5.13. FINAL POWER SUPPLY CHECK 5.13.1. Unplug AC cord and turn rotaryswitch to "SHUTDOWN" (OFF). 5.13.1.1. Disconnect "cheater" cord from CRl, H.V. Bridge and reconnect spade terminals to the H.V. Bridge. 5.13.2. Check and be certain that all switches (except Keyswitch) are "OFF" and the Variac is at "0". 5.13.2.1. Disconnect resistive load box from supply. 5.13.2.2. Connect correct test "head" to supply. 5.13.3. Disconnect scope probe from PWB 1,9 and post #2 on chassis. 53
  • 5.13.3.1. Connect scope probe ground to RFI filter bracket. 5.13.3.2. Connect probe tip to 1,22. This will allow viewing of Cd heater waveform (duty cycle). (2mSecldiv,10v/div,Line sync). 5.13.4. Connect the multi meter (-) to minus end of C 19 and (+) to top end of R7i2 (Temp diode voltage). Use 2v scale. 5.13.5. H.V. meter is still connected: negative to RFI bracket, (+)2KV to outside end of 10K, 50W resistors, and (+) 20v to minus end ofC19. Now, by switching meter between 20v and 2KV, the tube current and tube voltage may be observed respectively. Place air baffle over the three heat sinks. 5.13.6. With rotaryswitch "OFF", plug AC cord into line outlet. 5.13.7. Rotaryswitch to "OPERATE": Tube lights in 2-4 seconds. 5.13.7.1. Tube voltage should be near 1200v, for a 139, and around 2KV for a 100 or 156. Tube current should be 100+/-2mA (1.00+/-.02v on meter). Cd light should come "ON". See scope photo #5. 5.13.8. Tum rotaryswitch "OFF" momentarily. The voltmeter should read 0.82v+/-.03v (82+/-3mA). Cd light should go "OFF". 5.13.8.1. Tum rotaryswitch "ON". Cd light will come "ON".5.14. HE CONTROL 5.14.1. Test "Head" is set to cause the He Htr to come "ON" after a few minutes, then go "OFF" as the tube comes up to temp.5.15. CD CONTROL S.15.1. Allow tube voltage to stabilize at 925-99Sv for a 139,1 and about 1550- 1650v for 100 or 156. Will take 5-6 minutes. S.IS.2. Diode voltage (temperature) should start at about .6v and will be in the .35 to .42v range when tube is stabilized. 54
  • 5.15.3. Tube voltage should be stable, with <2 volt variation. 5.15.4. Observe scope trace of Cd Htr duty cycle. Should be 70-80% at start, and about 50% for a 139 and 35% for a 100 or 1 stabilizing. See scope #6. reasonably steady. 5.15.4.1. If waveform is steady with only an occasional "jump" continue with test.5.16. THERMAL LOCKOUT & SHUTDOWN TIMER CHECK 5.16.1. Tum rotaryswitch "OFF". Cd light should go "OFF", 1 green power light will remain "ON". 5.16.2. After 2 min, ] 6 sec. the tube should go out, and the red LED (temp lockout) will come "ON". 5.16.3. At 2 min. 51 sec. all lights should go "OFF". 5.16.4. Tum rotaryswitch back "ON". Green and red LEDs should come "ON". 5.16.5. After several minutes, red LED should go "OFF". Cd should come "ON", and tube lights again. 5.16.6. Complete checkout sheet and attach proper labels to the power supply. See that proper SIN & Model # are on the checkout sheet. Place checkout sheet in proper folder. 5.16.7. Apply RTV to terminals, 1,2,3,4,&7 of Module, and to Connector. Install red air baff1e over three heat sinks before placing cover on supply (one screw only). Put rotaryswitch in "SHUTDOWN" before placing on shelf. 55
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  • SECTION 6 LASER MALFUNCTION REPORTDATE,_ _ _ _ _ NAME,_ _ _ _ _ _ _ _TELEPHONEOWNER INFORMATION:COMPANY NAME,_ _ _ _ _ _ _ _ _ DIVISIONADDRESSCITY_ _ _ _ _ _ STATE,_ _ _ _ _ _ZIP CODE -------LASER SYSTEM INFORMATION: LASER HEAD POWERSUPPLYMODEL NUMBERSERIAL NUMBERMALFUNCTION INFORMATION:1. TOTAL OPERATING HOURS: ESTIMATED TIME METER- - -2. PLEASE CHECK OFF ALL APPROPRIATE MALFUNCTION SYMPTOMS BELOW: _ _ Cl - LASER SYSTEM WILL NOT START UP _ _ C2 - LASER SYSTEM SHUTS ITSELF OFF _ _ C3 - LASER TUBE WILL NOT LIGHT _ _ C4 - NO LASER OUTPUT ___ C5 - LASER HEAD ARCING OR EMITS SMELL _ _ C6 - POWER SUPPLY ARCING OR EMITS SMELL _ _ C7 - LOW LASER OUTPUT (POWER: mW) _ _ C8 - OUTPUT POWER FLUCTUATES (TIME PERIOD, MINUTES PER CYCLE ). _ _ C9 - HIGH OPTICAL NOISE: RMS% P-P% 57
  • 3. DESCRIBE MALFUNCTION: SOUND, VISUAL, SMELL, ETC. 4. DESCRIBE OPERATING ENVIRONMENT: VIBRATION, SHOCK, TEMPERATURE 5. DESCRIBE CONDITIONS PIUOR TO MALFUNCTION: UGIITS DIMMING, ETC. 6. LIST ANY COMPONENTS OTHER THAN LASER SYSTEM WHICH MALFUNCTIONED PRIOR TO OR SIMUL TANEOUSL Y WITH LASER 7. HAS TIllS LASER HEAD REQUIRED PRIOR SERVICE? 8. HAS THIS POWER SUPPLY REQUIRED PRIOR SERVICE? 58i i