Troubleshooting request: Pioneer Tx-6800

[caxton1476]

Got a Pioneer TX-6800 for basically nothing. Wasn't able to test before taking it home and was willing to give it a shot, hoping to use it with my Sansui AU-555a.

Maybe I got what I paid for?

Anyways, it produces a hum or buzz through the speakers when I connect it to the Sansui. In fact, that sound comes through whether the tuner is on or off. It happens regardless of which input I route it through, and regardless of the tuner settings. I've switched out RCA cables; no difference. And I've tried it through the tape in loop on a different receiver (a Realistic STR-2270); again, no difference. And it gets louder when I turn up the volume.

If I touch the metal case of both units at the same time, the hum gets just slightly quieter, but not much.

I haven't even connected an antenna to the Pioneer, at this point.

Thoughts? Suggestions?

 

[dr*audio]

Sounds like a bad ground.There should be continuity from the ring on the output jacks to the power supply ground and the chassis. If not, look for a broken wire or a burnt trace on the pcb. If none of this makes any sense to you, you need a technician.

 

[caxton1476]

I just opened up the case and noticed this:



Seems suboptimal.

 

[dr*audio]

I just opened up the case and noticed this:

View attachment 3644202

Seems suboptimal.

Can't read the bands on that resistor at that angle, but if it's larger than 100 Ohms I think it's not your problem. You'd have to look up the reference designator and find it on the schematic. It could be a "select at test." Removed if not needed. Unfortunate that they didn't print the reference designators on the silkscreen so you know which resistor it is in the circuit. You have to get the service manual, and look at the pcb layout to identify it.

 

[caxton1476]

Here’s a different angle.



I hear what you’re saying - the ground issue is likely the really problem.

Just to be clear, the resistor that’s bent upwards and the other one adjacent to it that seems to be missing entirely…

The other pic is the underside of the board beneath the RCA jacks. To my untrained eye, it looks like some copper traces have flaked off.

Yes, I’m a total novice here. Willing and, I hope, able to learn a few basic diagnostics and repairs. Especially given the lack of techs in my area (relatively remote region of northeast Iowa).

 

[dr*audio]

That trace doesn't look good. Scrape some of the solder mask off the trace on both sides of that section and measure the resistance.

 

[caxton1476]

Thank you for that suggestion! The multimeter read 0.6

 

[dr*audio]

Thank you for that suggestion! The multimeter read 0.6

That's not the problem, then. Please measure the ground continuity as I suggested.