PCE Duo/TurboDuo wiring schematic?

[Desh]

Did you check your ground line to pin 4?  I've seen grounds get screwed up from a corroded via and make the op amp not power up.

Yes.  I don't know why I forgot to mention that.  I have continuity to any ground on the board to pin 4.  I guess it's possible but far fetched that both amps were bad.  I'm looking into the rest of the circuit working backwards.  I just don't see why there would be a problem closer to the source if I have sound where I should at the last amp in line.

[BlueBMW]

In fact, I think both of the op amps share a ground that goes through a via that has a bad tendency to get corroded.  Let me try and find the thread....

[BlueBMW]

Hmmm.. guess it was something different...

http://www.pcenginefx.com/forums/index.php?topic=3249.msg232905#msg232905

Might have some useful info buried in there anyways.

[Desh]

In fact, I think both of the op amps share a ground that goes through a via that has a bad tendency to get corroded.  Let me try and find the thread....

Shit you are on to something here.  When I had the amp off I checked continuity and visually inspected the vias hidden underneath.  I also had continuity to ground from pin 4.  For shits and giggles I soldered a wire directly to ground and attached to pin 4 of op amp 506.  It's not a complete success but the sound output is quite a bit louder than it was before (still only about 1/2 of what it should be).  I will continue the quest as time permits tomorrow. 

Thanks again for all of the help.

[BlueBMW]

Sweet!  Hopefully you'll track down the issue really soon!

Also, not sure if it is your problem but there is a via right next to R322 on the top of the board... it goes through near IC503 pin 5.  It always seems to be a problem VIA.  Might be worth checking continuity through.

[Desh]

Sweet!  Hopefully you'll track down the issue really soon!

Also, not sure if it is your problem but there is a via right next to R322 on the top of the board... it goes through near IC503 pin 5.  It always seems to be a problem VIA.  Might be worth checking continuity through.

Before I removed the top op amp again to check the ground again (I did have continuity and low resistance, only about .14 ohlm) I looked at the via you mentioned here.  It did look a bit discolored so I tested it and it seemed to be fine then I re-tested it and the circuit to ground was open.  I repaired that via and fired it up.  Now I'm back to no sound.

I checked voltage again at the top amp and only have 1.2VDC on pins 1 and 3 and 2.4 VDC on pin 8.  I also then followed the circuit back to the first bank of amps and have the same readings.  So now after repairing a questionable ground I now have a power issue somewhere.

[thesteve]

small SMD transistor in the cap jungle by the heatsinks is your 8V source

[Desh]

small SMD transistor in the cap jungle by the heatsinks is your 8V source

Thank you thesteve!  Only 4.2 VDC from the emitter.  I pulled the transistor and tested it.  It tests bad.  Any specific specs I can use to replace it?  I have a bunch of spare PNP's laying around.

[thesteve]

It's a 100mA NPN

[Desh]

It's a 100mA NPN

Thank you!  I saw the arrow on the circuit board pointing in to the emitter and assumed it was PNP.  I'm a noob with this stuff and learning as I go.

[Desh]

MISSION ACCOMPLISHED!  I replaced the transistor, fired up the DUO and BAM!  Full on static free sound.  I really can't thank everyone enough for all of the help.  THANK YOU!