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Schematics for the Onkyo


Just to let you know that FixYa has sent the diagram of the A-8190 and that am checking possibilities. Let you know ASAP.

Kind regards.


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  • Louie  Role
    Louie Role Oct 06, 2008

    Hi again,

    A question pls, at what point did you measure the -18VDC, speaker terminals?

    yes, then most likely a problem with the output transistor pair as
    initially posted. Additionally, if it is only on one channel, then you
    can use the other channel as reference when doing voltage measurements
    or in passive/resistance checks.

    Good luck and pls postback updates.

  • Louie  Role
    Louie Role Oct 08, 2008


    Much appreciate the assist. I have to agree with you since this Onkyo is basically a DC amp. FixYa sent an email informing that the user asked that the schematic be forwarded to me. I did not post in the problem that I have a copy of the service manual/schematic but just mentioned that there are several models of the A-8190 (based on the primary of the main transformer). In any case, what I can not reconcile is where the user measured the -18V hence my question "at the speaker terminal?" Which is doubtful since this model uses (split PSU) +/- 60VDC. Assuming either the driver or the output is shorted, then the voltage across the speaker terminals would be greater than 18 closer to 60. The closest (but unlikely) possibility would be the +/- 22 Volts regulated supply of the NJM4558SE (Q519 or Q 520).

    Incidentally, here is the original post.

  • Louie  Role
    Louie Role Oct 09, 2008

    Thanks Dan for confirming my initial suggestion of checking Q701, and the 2SA1491 & 2SC3855 pairs as posted in the original Premium Problem.



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I don't have the info on the initial question/posting, but Onkyo systems I have worked on often have open driver transistors as well as shorted outputs. With one of the driver transistors open, the voltages tend to float to one side. The 18V you mention sounds like that is what is happening. have the initial asker replace the driver transistors (as a pair) just like the outputs.

Keep me posted.

Posted on Oct 08, 2008

  • ABRsvcs Oct 08, 2008

    Actually, if one of the drivers is open or one of the low voltage feeder resistors is open, this kind of offset is possible. Can you forward the schematic to me at

    I'll look into it a bit more and update this again.



  • ABRsvcs Oct 09, 2008

    After looking at the schematic, I see that this unit has a TA7317 chip. This is the "protection" chip and these are known for going bad. It is quite possible that the source of the 18V is this chip. have the asker change this IC. That may resolve the problem. Otherwise, lift the bases of each of the 4 output transistors and post the voltage readings on the 3 pads of each transistor here.




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