Advice needed JVC PC-55 bad channel output

I could use a little help here.
Grabbed another PC-55.
After 3 hours of use, the right channel has died. Sometimes it will "pop", come back, hum..ect , but it never comes back full for more than a few seconds.
It's not the speakers, or jacks, or cables.

Headphone output is fine, volume controls are good, not scratchy. That rules out the pre-amp.

I'm assuming the output capacitors may be weak, or a cold solder joint on the output board.

Any other suggestions as to where I can investigate?
Thanks

Cleaning all switches with deoxit or contact cleaner and working them should bring it back


Bad Boy Bill

baddboybill said:

Cleaning all switches with deoxit or contact cleaner and working them should bring it back


Bad Boy Bill

Click to expand...

also you have to get inside the box to clean them ,spraying into the openings in the front won't do much on these boxes because the buttons have extensions on the inside to reach the pc boards.

i also have spare switches if needed.

JVC Floyd said:

baddboybill said:

Cleaning all switches with deoxit or contact cleaner and working them should bring it back


Bad Boy Bill

Click to expand...

also you have to get inside the box to clean them ,spraying into the openings in the front won't do much on these boxes because the buttons have extensions on the inside to reach the pc boards.

i also have spare switches if needed.

Click to expand...

I've opened her up and completely disassembled. Removed the tuner board. I've cleaned the switches and volume control.
Everything is fine as far as that goes, if my controls were bad, then they would fail while using headphones. Not a hint of scratchiness.

I'll have to remove output cap board and power amp board next, check for bad solder joints and probably replace the output caps.

Won't be the first time I've had to do it, although usually it's in a much larger amp or receiver.

Have you checked headphone jack itself. It's common for corrosion to build up inside causing bad connections as well while nothing is plugged in


Bad Boy Bill

baddboybill said:

Have you checked headphone jack itself. It's common for corrosion to build up inside causing bad connections as well while nothing is plugged in


Bad Boy Bill

Click to expand...

I have had contact problems before on the headphone jack of my Fisher PH 480
I would check this on the JVC first
Good chance that the jack causes this issues

baddboybill said:

Have you checked headphone jack itself. It's common for corrosion to build up inside causing bad connections as well while nothing is plugged in


Bad Boy Bill

Click to expand...

You know, I *think* that may be the source of my problem.
I admit I ignored the HP jack.

I had the thing completely disassembled , I checked the caps, re-flowed solder joints on the board, still not good.
Right channel would lose volume, get distorted, noisy, pop and hum, then come back, cycle all over again.

On an amp, this is a classic sign of failing caps or speaker relays, however I never considered the HP plug.

I read your post, sprayed some de-oxit in the jack, worked a HP adapter in and out a number of times, it seemed to improve, but wouldn't last.

I'm going to remove the jack, try to disassemble it and give it a really good once over, I'll make a jumper to test the unit with out the jack, and if it's bad, I'll have to find another.

Thanks for the tip.

UPDATE
Well, the headphone jack is not the problem, nor the connections to and from.
I jumpered the jack to bypass it, and my problems still continue.

I know it's not the pre section, as using headphones, there's no problems. Taking an adapter and running the output to a pair of computer speakers, the unit will run for hours with no problems.

The only area left is the power amp itself. It's at the very bottom but I've no choice, this unit is too minty to give up on.
Since there are no relays, cold solder joint somewhere on the amp board seems to be the most likely culprit.

Update 2

Looks like the problem is with the right channel amp IC
Measuring the voltage I've got nothing on the IC's output. Left Channel IC gives me 1.1 volts on the output, right channel nothing.
I need to disassemble even further, so I can look up the IC and get the pin-outs so I can check the input voltage.

Am I having fun yet?!?

Riker digs up an old one. Was the issue ever solved? My 919 I got today has a weak left channel and I am researching.