Onkyo TX-SR702 no audio after channel repair

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  • akarta
    Member
    • Nov 2015
    • 16
    • United Kingdom

    #1

    Onkyo TX-SR702 no audio after channel repair

    Really strange one. Got this amp with digital noise coming from all channels. BAD cap on 12V rail and burned via on -12V rail causing -7V and +7V rails missing, audio noise and "SP CONFIG" message (thinking that MIC is plugged in then it is NOT, but before I replaced cap and fixed rails I have accidently left it ON with output transistors for rear channels hanging in air (NOT HEATSINK ). One channel blew. After further inspection found a LOT of caps out of range on DSP and Processor boards. Replaced every single one that did not pass my ESR test(almost all).Got receiver back together (Output stage repaired as well) and to my surprise NO AUDIO. Output relays do click in and could hear hissing. No protect messages come on FL display. Did diagnostic test 4-21 and above. All channels report "Protect NG". In normal mode if I press Pure Audio button I can hear music out of my speakers if volume set to 100 and I have my ears against speaker. Now the measurements:
    VOLH: 0.00V (service manual does not tell that should be good range)
    PROTECT: 0.00V (0 means protection not triggered, 3.3V do trigger protection if I inject voltage )
    THERMAL: 0.00V Don't know that value should be
    I have notice that processor is keeping MUTE line HIGH. If I pull it LOW I am getting audio on PURE AUDIO mode, but not in DIGITAL mode. Pressing mute on remote I get no audio but MUTE message on display.
    Spend 3 days on this amp and now I hit the wall. Anyone had something similar? That should be VOLH value?
    Attached Files
  • CapLeaker
    Leaking Member
    • Dec 2014
    • 8187
    • Canada

    #2
    Re: Onkyo TX-SR702 no audio after channel repair

    Make sure nothing is stuck in the headphone jack. Maybe see what it does with a head set connected. Also look at the the power rails on the digital board to see if all the chips power up. Next you could try to press on components or use heat and cold on certain IC.
    Last edited by CapLeaker; 05-02-2022, 01:19 PM.

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