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Yamaha Home Theater Receivers woes

Discussion in 'Troubleshooting and Repair' started by SandingValve, Jul 13, 2015.

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  1. SandingValve

    SandingValve

    2
    0
    Dec 5, 2010
    I have a pair of Yamaha receivers that have different issues:

    Yamaha RX-V1200: This unit powers up and operates great until it warms up some. After that, all the preset surround sound effects, center channel and subwoofer outputs go dead- no signal/no sound. I suspect a bad connection somewhere, already checked ribbon connections. Bad/cold solder joint(s)?? But where to look??

    Yamaha RX-V494: This unit tries to power up and immediately shuts down. I've tried to put it in diagnostic mode, but it will only hold on long enough to display 'PS' followed by a quickly fading numerical value as the unit shuts down.

    Any help on either unit or both would be wonderful. Hate tossing a decent unit when something so simple as a cold solder joint or bad capacitor is to blame.

    Thanks,
    SV
     
  2. Martaine2005

    Martaine2005

    2,538
    681
    May 12, 2015
    My initial checks would be the for spillage. Some sugary spillages are dry when cold and liquify as they heat up
    causing a short.
    But more than likely a component is overheating and the circuit shuts down. You can spray some 'freezer' on the transistors and try and see what is heating up quickly.
    It's late now, but I will have a look for the service manual tomorrow.

    This is more than likely the power supply or the output stage. First check the psu capacitors and then check the output transistors.

    Some good quality pictures of the boards would be an advantage and some more info on the first amp you posted.
    Like, how long before the centre channel shuts down?
    Are there leds on the presets that still work?
    Do the other channels continue working properly?
    Does it make any noise before the problems occur?
    Can you smell anything strange etc?

    Martin
     
  3. chinathermostats01

    chinathermostats01

    3
    0
    Jul 16, 2015
     
  4. chinathermostats01

    chinathermostats01

    3
    0
    Jul 16, 2015
     
  5. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    As for the Yamaha RX-V494:
    "PS" in the Yamaha jargon means "power supply DC fault",the value is the "deviation amount from normal" .

    You have to get a service manual and check all DC voltages in the unit(there are quite a few ...)
    There is a way to disable the the shut-off ,you should look at the service manual for that.
    Do that at your own risk ! it can cause more damage(but that is the way to check and repair)

    If you are lucky it could be an easy fix...cap, zener, regulation transistor, linear reg. etc. in the power supply.

    !
     
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