rx-v2090

Yamaha RX-V2090 Repair help needed...

Hi everyone.
I've been away for a long time now.
I'm trying to repair a Yamaha receiver (rx-v2090).

Strange problem, i'm not sure if this is a well known issue or a rare one:

Receiver works fine except sometimes (Usually after being unplugged for a day or so - but not only in these circumstances) it does not turn on (lights up and shuts down after less than a second). The problem occurs even with no line in and without any load (no speakers).

When the receiver does turn on it can work perfectly for hours without any problem.

I'm guessing its some kind of "false positive" in the protection circuit (maybe a cap?) but i'm not sure how to go about tackling this.

got the full service manual for this amp but it's too beefy to attach. I'm attaching only the schematics (and I had to split these into 2 files so I could upload it).

Any help is welcome.

thanks in advance!
 

Attachments

  • yamaha_rx-v2090_sm_part1.pdf
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Receiver has a primary power relay on the "Sub power supply board".
This is the relay that "clicks out" when the amp goes out.

unfortunately the command for the relay's transistor come straight from the main CPU itself.

Since the problem seems to happen more when the receiver is left unplugged I was looking for a bad cap. However now that the CPU is involved it literally could be anything.

Any ideas anyone ?
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
I can't locate the PSU unit on those schematics but from your description it would seem that a Microcontroller
controls the startup sequence but is not always operating, due perhaps to no 5V power.

This micro can need to be powered 24/7 and may use a "Super Capacitor" of about 0.47F to keep memory
whilst power is off. These can fail or lose capacity so that they don't hold charge for long enough.
That may prevent the control circuit starting up, charging the cap. and powering the MCU etc.
Maybe it's worth checking first if there is a supercap or battery and how the power is maintained or not in
stand-by when the power is off for a few days. It wouldn't be the first time some funny symptoms have
shown up on a receiver due to dependency on fragile parts like batteries.