1. An Electronic Troubleshooting Project
Recently, I was given a Yamaha RX-V367 surround sound amplifier by a friend of mine.
The amplifier had been
damaged by a power
surge (lightning
strike?) at his house,
and when
homeowners
insurance replaced the
amp, my friend,
knowing I am
experienced in
electronic
troubleshooting and
repair, gave the
damaged amplifier to me.
As most who have done electronic troubleshooting work on consumer audio products
know, amplifiers produced over the last decade or longer use a microprocessor in the
amplifier to monitor the sub-systems of the unit. If the microprocessor detects a problem
in the system, it will not allow full power into the amp. Typically, a damaged amplifier
will power on for a few seconds, the microprocessor will detect a problem, and the unit
will shut itself off.
This is exactly the
first situation I
encountered; the
amplifer’s internal
microprocessor
would not let the amp
power up.
I removed the top
cover of the amplifier
and the first
indication of damage
was a blackened area
around the HDMI
output connector on
the HDMI input/output board. I did not have a schematic for the unit, so my first step
was to prove that the problem was caused by damage to the HDMI output circuit.
Reasoning that the unit might power up with the board out of the circuit, I disconnected
the ribbon connectors going to the board and powered on the unit. The amp now ran for
approximately 10 seconds, with lights and front panel indicators, before shutting itself off

2. again. This indicated to me that the microprocessor no longer read a damage fault, but
turned itself back off because the HDMI board was out of the circuit.
I used the electronic traces on the board itself to trace back from the HDMI output
connector on the edge of the board to the IC that routed signals to the output. While there
were four HDMI input connectors and associated circuitry on the board, there was only
one HDMI output where these signals were routed - regardless of what HDMI input was
used,
all inputs used a single HDMI output. It was a simple matter to find the HDMI output IC.
I reconnected the board, put my finger on the HDMI output IC, and pushed the power on
button, and within two seconds, the IC got hot enough to burn my finger, before the unit
switched itself off once again. It was obvious that the HDMI output IC had been
internally damaged (shorted - note the small black burn mark on the center right area of
the IC, immediately over the digits 00).
I used an industrial razor blade to carefully cut the traces around the HDMI output IC,
removing it from the circuit. Close inspection of the removed HDMI output IC showed
small burnt areas on the surface of the IC, indicating internal damage. Since the power
surge had obviously entered the system at this point, and understanding that damage was
probably limited to this portion of the circuit, I then
reconnected the board, and turned on the power. The unit powered on, and all functions

3. with the exception of the HDMI output tested okay. I now have a functioning Yamaha
RX-V367… sans one HDMI output.