This document provides instructions for adding an on/off LED indicator to Hakko 936-x temperature-controlled soldering stations. The modification involves drilling a hole in the front panel and PC board to mount a green LED. A resistor is also added to the PC board to limit the LED current. The LED will illuminate whenever power is applied, providing a visual status indicator that was lacking in the original design. The instructions include diagrams of the front panel and PC board layout and provide detailed steps for implementation.

1. Note: " " = CKT GND
HAKKO 936 - Schematic
Rendered by: Tom Hammond - NØSS 26 MAR 2011 v1.7
MAIN PC BOARD
AC ON/OFF PC BOARD
VREF
VREF
VREF
VREF
IC2B
OUT
LM324
IC2A
OUT
LM324
IC2D
LM324
OUT
TRIAC DRIVER
IC1
NC
B
A
C
G
F
E
D
1
3
2
4
8
7
6
5
VREF
LM324
OUT
U1C
VEE
VCC
VCC
VEE
AC
Q1
R4
T1
T2
G
IC2C
ZD2
ZD1
10
9
8
11
+
_
4V+
V-
R10
C3
C2
C1
R1
D3
R3
C4
C9
R13
R2
R14
1
2
3
+
_
+
_
R7
TEMP
CTRL
5
6
7
R15
R8
R5
C5
R9
R11
SENSOR
PINS
SOLDERING
IRON PLUG
SLEEVE GND
HEATER
PINS
R17
R16
C6
R12
R6
C7
CAL
CTRL
12
13
14
HEATER
LED
1
3
5
HANDSET
TIP GND
BLK
WHT
GRN
D1
D2
HOT
NEUT
GND
CHASSIS
GND
CHASSIS GND
SOLDERING IRON/CHASSIS GND
CHASSIS
GND
POWER
XFMR
NEC AC05D
5A TRIAC
1k
NEC* µPC1701C
Zero Volt Switch
NEC µPC324A
Lo-Pwr Quad OpAmp
220µF 50V
47µF 16V
47µF 16V
5.1Zv 500mW
5.1Vz 500mW
680
360 2W
metal film
15k
.01/50V
.01/25V
1k8
1k0
5k0
ALPS RK09L
1140A65 5K
(502B) LINEAR
390 1%
1M0
.01/25v
130k
1%
27k0
1%
300
HANDSET
SOCKET
1N4148
100k
5k1 1%
24k0
.01/25V
1k0 1%
180k 1%
66k5 1%
1k2
0.1
25V
1N4007
120VAC 24VAC
120VAC 2A

2. HAKKO 936 TEMPERATURE-CONTROLLED
SOLDERING STATION PC BOARD LAYOUT
Rendered by: Tom Hammond, NØSS 26 MAR 2011 v1.7
PC BOARD AS VIEWED FROM THE COPPER (SOLDER) SIDE

3. HAKKO 936 TEMPERATURE-CONTROLLED
SOLDERING STATION PC BOARD LAYOUT
Rendered by: Tom Hammond, NØSS 26 MAR 2011 v1.7
PC BOARD AS VIEWED FROM THE COMPONENT SIDE

4. HEATSINK
HAKKO 936 TEMPERATURE-CONTROLLED
SOLDERING STATION PC BOARD LAYOUT
Rendered by: Tom Hammond, NØSS 26 MAR 2011 v1.7
PC BOARD AS VIEWED FROM THE COMPONENT SIDE
HTR
LED
JP1
R4
R13
R6
R7
R2
R8
R12 R10
R15
D1
D2
C1
C3
C7
C2
Q1
IC1
IC2
T1 T2 G
N/C
N/C
+
+
+
+ VEE
VEE
VCC
VCC
VCC
VREF
CN1
FG
1
2
3
4
5
VR2
PVR1K A

5. HEATSINK
HAKKO 936 TEMPERATURE-CONTROLLED
SOLDERING STATION PC BOARD LAYOUT
Rendered by: Tom Hammond, NØSS 26 MAR 2011 v1.7
PC BOARD AS VIEWED FROM THE COMPONENT SIDE
1k
100k
47uF
16v
47uF
16v
220uF
50v
AC05D
B1081
C324C
C1701C
27k 1%
5.1k 1%
1.8k
24k
680
130k 1%
390 1%
0.1
25v
300
5k
1N4148
1N4148
J

6. C1 220uF 50V
C2 47uF 16V
C3 47uF 16V
C4 0.01 (103) 50V Ceramic
C5 0.01 (104) 25V Ceramic
C6 0.01 (104) 25V Ceramic
C7 0.1 (104) 25V Ceramic
C8, C10-C13 n/a
C9 0.01 (104) 25V Ceramic
D1 4N4148 Small Sig Sil, or similar
D2 Small Sig Sil, or similar
D3 1N4001, or 50VDC (or higher) @ 1A
IC1 NEC* PC1701C, Zero Volt Switch
IC2 NEC* C324A, Lo-Pwr Quad OpAmp
Q1 NEC AC05D 5A Triac
R1 360 2W 5% metal film
R2 1.8k 1/4w 5% carbon film
R3 15k 1/4w 5%
R4 330 1/4w 5%
R5 1.0k 1/4W 1% metal film
R6 27.0k 1/4W 1%
R7 5.11k 1/4w 1%
R8 390 1/4w 1%
R9 66.5k 1/4w 1%
R10 680 1/4w 5%
R11 180.0k 1/4W 1%
R12 130.0k 1/4W 1%
R13 100k 1/4w 5%
R14 1k 1/4W 5%
R15 24k 1/4w 5%
R16 12k 1/4w 5%
R17 1M 1/4w 5%
ZD1 5.1Vz 500mW,
ZD2
PVR1 TEMP ADJ POT - ALPS RK09L1140A65 5K
(502B) LINEAR
VR2 CAL TEMP POT - Bournes 3362P-1-501LF,
see note below
* NOTE: NEC, is now part of Renesas Electronics Corp.
NOTE: In the 936, the CAL TEMP pot is 300 Ohms, however
we were unable to find a pot in this physical format rated at
300 Ohms, so a 500 Ohm device has been specified as a
suitable substitute.
4N4148
P
carbon film
carbon film
metal film
metal film
metal film
metal film
carbon film
metal film
metal film
carbon film
carbon film
carbon film
carbon film
carbon film
5.4Vz (measured)
5.1Vz 500mW, 5.2Vz (measured)
μ
μ
CAL TEMP CTRL
HAKKO 936-x PC Board Parts List

7. ADDING AN ON/OFF LED TO HAKKO 936-X
TEMP-CONTROLLED SOLDERING STATIONS
by: Tom Hammond, NØSS 03/09/2011, v.4.1
Is it turned ON or not?
By golly, it WAS, but how could you tell?

8. ADDING AN ON/OFF LED TO HAKKO 936-X
TEMP-CONTROLLED SOLDERING STATIONS
by: Tom Hammond, NØSS rev. 03/09/2011
The Hakko 936-x line of temperature-controlled soldering stations has one flaw. It offers no real POWER ON/OFF
indication. There is a red LED which illuminates when heat is being applied to the tip of the iron, but it lights
ONLY when heat is being applied. As a result, if you glance at the station when no heat's being applied to the tip,
you might think the device is actually turned off. I've walked off and left the soldering station running for several
days because the red LED was extinguished when I looked at it, even though power was still applied.
Here's a fairly simple-to-install mod which will add a green LED to the right hand side of the front panel on the
936. This LED will be illuminated any time power is applied to the soldering station.
1. Remove four (4) screws from the bottom of the case, and lift off the case top.
2. Remove the temperature control knob and carefully loosen the setscrew in the temp-lock mechanism.
Remove the setscrew and nut and set them aside in a safe place.
3. Lift the front panel/PC board combination out of the case and carefully desolder the 6-pin (five [5] pins and
one [1] lug) soldering iron cable connector from the PC board. USE CARE HERE.
4. With the 6-pin connector free of solder, hold the front panel on its sides with both bands and use your thumb
to press on the shaft of the temp. control pot to push the PC board assembly away from the front panel.
4. Using Figure 1 (see next page), a scale drawing of the front panel, as an overlay of the drilling template, lay
the template onto the front panel and CAREFULLY center punch and then drill a 3/16" (4.75mm) hole. Then
use a much larger (about 1/2" / 13mm) bit (hand-held), or a hand reamer bit, to 'hollow' out a bit of the back
side of the hole just drilled to allow the new LED to extend out the front of the panel just a small distance.
5. Refer to Figure 2 (next page),SOLDER SIDE of the PC board. Using a #60 (0.040") or smaller drill bit, drill
four (4) holes, as indicated, to accept the new LED (green, T1-3/4 size), and the current limiting resistor
(R ,3.0k to 3.9k 1W, the exact value is not terribly critical, a metal film/oxide resistor was selected for its
smaller physical size), Mouser Electronics #
6. Once the four holes have been drilled, use a sharp knife blade and scrape away the solder mask from the
two points indicated in Figure 2. Once these two points are cleaned of solder mask, tin the bare copper.
7. Regarding the LED... generally, there is a flat side on the base of the LED body to indicate the CATHODE
side. Additionally, on most (though not all) LEDs, the CATHODE lead is the SHORTER of the two (assuming
a new LED with un-cut leads).
8. ALL REMAINING STEPS REFER TO FIGURE 3 (next page). Install (BUT DO NOT SOLDER) the LED with
its CATHODE lead in the hole indicated by the illustration. DO NOT BEND THE LED LEADS AND DO NOT
SOLDER YET!!!
9. Insulate and bend the leads of R at right angles and at appropriate distances to allow R to drop into its
mounting holes. Raise R about 1/8" (3 mm) above the PC board and solder ONLY the lead which is
connected at the top of the resistor to the copper land.
10. BEND the bottom lead of R to the right, and around the ANODE lead of the LED. Use wire cutters to trim
any excess lead length once the lead has been bent around the LED anode lead. DO NOT SOLDER YET.
11. Temporarily re-assemble the front panel and the PC board, ensuring that the 6-pin connector is properly
inserted into its PC board holes. Ensure that the front panel and the PC board are well mated and parallel to
each other, then press the green LED into its hole in the front panel so it seats properly.
12. With the new LED in place, solder the junction of R and the LED anode lead.
13. Bend the CATHODE lead of the LED flat against the PC board and so it touches the adjacent area of the PC
board from which you scraped away the solder mask. Solder the LED CATHODE to this point on the PC
board.
14. Re-solder all (6) of the 6-pin heating element connector leads.
15. Reassemble the soldering station.
L
L L
L
L
L
594-5083NW3K900J (3.9k 2W metal film).

9. LED (shorter)
Cathode lead
Rev.: 03/09/2011 v4.1
Cut away these two sections
of the template to allow the
template to fit over the temp
control bearing & heating
element connector
Drill 3/16"
(4.75mm)
hole here
Figure 1.
HAKKO 936-X T/C Soldering Station Front Panel
(Viewed from the FRONT SIDE)
Figure 1 - Cut out the template at right. Then cut out the
two marked areas so the template will clear the temp.
control bearing and the heating element jack when laid on
top of the front panel. Tape the template into place on the
FRONT SIDE of the front panel. CAREFULLY center
punch the point where the hole is to be drilled. Drill a
3/16" (4.75mm) hole from the front. You may want to first
drill a smaller 'pilot' hole and work up, in steps, to the
larger final hole diameter. This will often help reduce the
chances of paint chipping, etc. Then, use a larger (hand-
held) bit (or a reamer) from the back side to 'hollow out' the
back of the hole just enough to allow the tip of the new
LED to extend out the front of the front panel to the same
extent as that of the red LED. If the green LED is allowed
to protrude a bit farther than the red LED, it will be more
readily noticed as you use the device in a normal working
environment.
Green
T1-3/4
LED with flat
(cathode) side
away from R
and bent flat
against PC
board to touch
cleaned and
tinned land)
L
Anode
(longer lead)
Limiting
Resistor (R
(Insulate Leads
& raise above
PC board)
L)
Figure 2. Hakko 936-x PC board preparation
(as viewed from the of the PC board)SOLDER SIDE
Figure 3. Hakko 936-x PC board - New Components
(as viewed from the of the PC board)SOLDER SIDE
0.70"
(17.8mm)
1.33"
(33.8mm)
Bend existing
power resistor
out of the way
(TOP of PCB)
Drill four (4)
holes (.025" to
.04" dia.) in
PC board at
points shown
After drilling,
scrape solder
mask away
from this part
of the land.
Scrape solder
mask away
from this part
of the land.