Fisher 200-T has no audio on left channel on main speakers or headphones

[maples]

Hello,
I was given an old Fisher 200-T receiver/amplifier from my grandparents. I set it up last night, and am having some issues with the left audio channel. The audio level is extremely low, barely discernible but it is there. The right channel works (mostly) as expected.

Troubleshooting/diagnostics I've tried:

• Swapping the speakers. The issue is on the right channel in the receiver/amplifier itself, the speakers are fine.
• Testing different inputs. I tried with FM radio (both tuning into a station and listening to static) and with a record player. The behavior is the same for both inputs.
• Plugging in headphones. The issue is there, too. The right channel comes through clear, but the left channel is very quiet.
• Fiddling with the Balance knob. The balance knob seems to have no effect on either the left or the right, except when I turn it all the way to the right, then the right speaker intermittently cuts out.
• Fiddling with the Monitor, Muting, Mono, and Loudness buttons. None of them caused any significant change in the left audio output.
• Fiddling with the Bass/Treble knobs. No luck there.
• Fiddling with the volume knob. No dice there either. I didn't crank it all the way to max, but at no point along the dial that I tried did the left channel get above a whisper.

It came with a copy of the Service Manual, which has electrical schematics. I played around with basic electronics in middle school, so I can name most individual components, but I am no electrical engineer and have very little understanding of how amplifiers or other circuits work in the real world. I can post photos of them, though, if that would be helpful. (And as an aside, if there's an archive of service manuals like this somewhere, I'd be happy to upload them there too!)

Any ideas on where I should start troubleshooting? I've read in other places that replacing all the capacitors is something other people have done, does that make sense to try with the symptoms I've described above?

 

[Sterling245]

I think the issue you are describing is most definitely a capacitor problem. These early SS Fisher units are known for bad caps and I have worked on many with that exact symptom - new caps almost always solved it. The whole unit needs a recap if you are planning to use it, but I would be most suspicious of/change first the output capacitors (2 large ones on the top side of the chassis) as well as any in the preamp/tone control circuit. If I had to guess, the problem is likely in one of those two places.

 

[JamesML]

Agree with Sterling245. I had a similar problem with a Fisher 440-t which is similar in many respects to the 200-t.
Low volume signal in one channel.
Found a faulty cap in the pre-amp board. Recapped the board and all fixed ok.

 

[maples]

Thanks for the input!

I took a look inside and didn't see anything obviously wrong with any of the capacitors, so I think I'll go ahead and replace the two large output capacitors and the four capacitors on the preamp board.

I think I've found suitable replacements for each of the capacitors, but I'm in unfamiliar territory -- would one of you mind checking my shopping list and see if these look correct?

• 2x 500uF (pre-amp board): https://www.digikey.com/en/products/detail/vishay-sprague/TVA1209/5612814
• 2x 4uF (pre-amp board): https://www.digikey.com/en/products/detail/vishay-sprague/TVA1402/5612912
• 2x 1000uF (large unmounted metal cans): https://www.digikey.com/en/products...draloric-bc-components/MAL205658102E3/5632999

Also, do I need to worry about those two white 0.33uF capacitors? I'm not sure if those are the kind that go bad or not.

 

[Sterling245]

Those should work, but I would recommend going for radial-leaded caps instead of axial just to make things easier for you. These should work:

For replacing 500uf: https://www.digikey.com/en/products/detail/nichicon/UHE1C471MPD6/58926

For replacing 4uf: https://www.digikey.com/en/products/detail/rubycon/50YXM4R7MEFR5X11/21739058

No need to worry about the white capacitors - they likely aren’t bad.

 

[maples]

Okay, I finally got around to replacing those capacitors tonight. The good news is, I didn't break anything! The bad news is, it's still giving the same behavior as before.

Any thoughts on what else I should check? I see two more capacitors that I could replace on the power amplifier boards, I could get replacements for those and see what happens.

I did try disconnecting the Balance knob out of curiosity (it acts fiddly, it doesn't actually seem to work for the functional Right channel unless you apply pressure on it in a certain way) I de-soldered the ground connection from it, and that didn't make any difference, so I don't think the balance control is causing problems.

 

[Sterling245]

I'd definitely replace the 2 on the power amp boards. Also, have you recapped the board labeled "Audio Control Amplifier"?

 

[maples]

I took a look at the Audio Control Amplifier board, but there don't seem to be any electrolytic capacitors on them. Unless those green ones need replacing regardless?

There are a few more electrolytics on the Power Amplifier boards I didn't notice at first glance, so I'll add those to my list too.

EDIT: I studied the schematics a bit closer and found 2 more capacitors on the preamp board I'd missed, tucked in line with a group of resistors. Looks like I'll be removing the pre-amp board again, though I'm not looking forward to de-soldering that long line of pins a second time...

 

[Sterling245]

You should be good on the control amp then. I just glanced at the schematic and saw capacitors, not realizing there were no electrolytics! Definitely change the ones on the power amp board though, they could be causing the problem. A quick way to find that out would be to swap the input wires to the amp boards and see if the problem stays in the same channel.

Another thing that likes to cause problems in these early Fishers is the socketed transistors. You could try pulling them and cleaning the sockets with Deoxit. I have seen dirty sockets cause very low/no audio before.