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Yamaha audio receiver no power

Discussion in 'Troubleshooting and Repair' started by Jim Smith, Nov 24, 2014.

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  1. Jim Smith

    Jim Smith

    2
    0
    Nov 24, 2014
    Hi , would appreciate help troubleshooting source of problem:
    Problem: Yamaha HTR-5990 receiver no power;
    Background: The night it stopped a set of speakers was not working, played around and came back on, I believe wires were touching (it was on other side of room, wires connected during cable run) and the whole system just shut off later that night.
    All wires have been removed from exterior, will not power up at all. When main power button pushed you hear click and click. I believe this is Yamaha's power protection kicking in.
    Opened up and a fuse by the power in was blown (#314 10A/250). Replaced but did not make a difference (did not blow again).
    On circuit board where power receptical attaches it reads 120V AC
    On circuit board the contacts for the wires leaving to go to transformer reads 0.05 AC, so power not going to main transformer, issue is on standby power supply circuit board.
    Nothing looks blown/burned/ or capacitors bulging.
    That's as far as I can go. Any help greatly appreciated.
    fyi, googled yamaha power protection bypass and if the bypass for this model is correct (hold straight / effect button and power on button together ) it doesn't make a difference. LCD doesn't come on.
     

    Attached Files:

  2. shrtrnd

    shrtrnd

    3,734
    478
    Jan 15, 2010
    It would help if you could locate a schematic. With what we know so far, you have an open circuit somewhere. Whatever fried is probably in the power supply section.
    If you can't find a schematic and see no physical damage, I'd start tracing the 120VAC in, until I find where you lose it.
    Any possibility there's another fuse in there separate from the input power fuse?
     
  3. Jim Smith

    Jim Smith

    2
    0
    Nov 24, 2014
    haven't been able to find schematic. There is another small fuse, but it tested ok. I have attached photos of the power board. Top and bottom. The pencil shows position of the power in. I haven't traced a circuit board before, could you assist. fyi I have removed the original fuse that was bad in the top view photo. Much appreciated. _F9A7945.jpg _F9A7945.jpg _F9A7942.jpg _F9A7947.jpg
     
  4. shrtrnd

    shrtrnd

    3,734
    478
    Jan 15, 2010
    You've got a voltmeter, I assume it's a multimeter. The fault could be anywhere, but from scratch, the first thing I do (with the board unpowered, as in the picture), is to check the power-related semiconductors. Your three-terminal semiconductors on your board. Use the ohm function, and look for an open on those three-terminal semiconductors, as they experience the the most susceptability to power damage. (That semiconductor attached to the heat sink, and the transistors. All black packages with three terminals.) The second most vulnerable devices are capacitors, if one of them burned open. This is all just preliminary, easy checks I do when I suspect an open device. Most troubleshooting is done with tracing voltages on the board, but in this case, you've already got the board out, and I'd check for open-circuit with an ohmeter as a first option. While you're doing this, take a good look at the devices
    on the board, and see if you can visually see a burned or damaged device. Good luck. You'll probably get other ideas from other people on this site to help you with this.
     
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