Pioneer VSX-919AH Phase Control blinking (AMP Overload?)
Good day folks. I found a Pioneer VSX 919 receiver in the trash pile and I thought I'd give it a whirl and try and fix it just to prove that I can and pass the time away....after my colleague gets bored of it, since he usually likes taking stuff from me so he can get all the credit, which he just did >_>
The problem is that the "Phase control" indicator flashes and the amp turns off, which according to the service manual which you can get here (pages 43 and 44 - too large to upload) indicates an "amp overload". The operating principle is shown on page 44. Not entirely sure how it all operates, but basically the base of Q5019 shouldn't get pulled low. If it is, Q5019 becomes conductive, which drives the base of Q5020, which then pulls pin 6 LOW, signaling the fault to the processor (which we assume functional at this point). The full schematic is on page 100. Problem is I can't quite figure out WHY that pin gets pulled low and what causes the issue. Mostly these VSX amps have problems with their DSP chips and I wrote a post about one some time ago, but this one is a bit different and looks like the problem lies in the amp section which might just be doable.
Haven't done any in-depth measurements myself yet and I couldn't find a pinout for the PAC014a amp modules, although I DID manage to find one for a STK442 which according to some chaps is close enough, so I at least know what those pins do. I wonder if removing the modules entirely should cause the amp to stay on. Any ideas how we should proceed ? Cheers and thanks !
The problem is that the "Phase control" indicator flashes and the amp turns off, which according to the service manual which you can get here (pages 43 and 44 - too large to upload) indicates an "amp overload". The operating principle is shown on page 44. Not entirely sure how it all operates, but basically the base of Q5019 shouldn't get pulled low. If it is, Q5019 becomes conductive, which drives the base of Q5020, which then pulls pin 6 LOW, signaling the fault to the processor (which we assume functional at this point). The full schematic is on page 100. Problem is I can't quite figure out WHY that pin gets pulled low and what causes the issue. Mostly these VSX amps have problems with their DSP chips and I wrote a post about one some time ago, but this one is a bit different and looks like the problem lies in the amp section which might just be doable.
Haven't done any in-depth measurements myself yet and I couldn't find a pinout for the PAC014a amp modules, although I DID manage to find one for a STK442 which according to some chaps is close enough, so I at least know what those pins do. I wonder if removing the modules entirely should cause the amp to stay on. Any ideas how we should proceed ? Cheers and thanks !
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