Yamaha RX-V371 power supply protection shuts the unit

Discussion in 'Technical Repair' started by CrackerJack, Jul 3, 2016.

  1. CrackerJack

    Thread Starter New Member

    Jul 3, 2016
    1
    0
    Hello guys.

    So, I have the forementioned Yamaha RX-V371 AV receiver and during the last month it keeps experiencing strange symptoms.

    1. When left turned off for some hours (say overnight) it turns ON only on ~third attempt, when it can't - it clicks with relays a couple times and goes into protection with "PS PRT xxxL" (xxx<=100[units] as per service manual). If it is finally on - it stays on normally, as if something heats or charges up enough for the thing to function.

    2. And the most annoying one - when any HDMI input (ps3, ps4) is used it randomly shuts down with the same "PS PRT" message before flickering video and audio for a couple of times. Not even remotely sure how this can be related to that. And yes, I tried different cables and different devices.

    When in service mode I observe the detection
    >PS:126 DC:058
    DC is always steady 58 while PS fluctuates in range [105-128], doesn't stay constant ever.

    PS: Power supply voltage protection detection Detected: AC2, ±12A, S9, +7D, +5A, +5I, -VP
    Detection port: 93 pin (PS_PRT) Normal value: 101 to 155 (Reference voltage: 3.3 V=255)
    DC: Power amplifier DC (DC voltage) output is detected.
    Detection port: 87 pin (DC_PRT) Normal value: 27 to 88 (Reference voltage: 3.3 V=255)
    * If PS or DC becomes out of the normal value range, the protection function works to turn off the power.
    The input AC voltage is rather steady 220-224v, plus the unit is plugged into UPS (surge protection outlet, not battery).

    I'm not really an electrotechnician when it comes to soldering boards and the most I can do is visually tell a blown elecrolytic cap from the normal one. And some rudimentary skills at using multimeter for probing voltages.
    I'll try taking the unit apart shortly once it goes into protection one more time and annoys me enough to do so, but if anyone has guesstimates on where to look - that would be most great.

    Any help on that is and will be appreciated.

    Best regards.
    Alexey.
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,750
    760
    Welcome to AAC.

    First check inside for bulging capacitors.
     
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