Fisher's Sony r2r

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walyfd
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Fisher's Sony r2r

Post: # 24737Post walyfd »

OK, continuing the woe in a new thread.

Those following, Fisher used the first consumer Sony 555A r2r in the President and Executive from 59 to 61. They sound great when working and running through the Fisher amp but it's also a PORTABLE unit with its own amp and can be hooked up to external speakers. Owners manual says it's 48 lbs in carrying case!!!

Anyway, issue is no right channel output on playback. I rolled tubes, checked wiring but I think it's a cap or something else. Both meters deflect in playback when it's turned on. Only left channel plays back. Not the heads because it has both 2 and 4-track heads. I switched the leads on the 4-track head and got output from the lower head leads hooked to the upper track.

Microphone plugged in, unit in STEREO RECORD, both meters deflect and sound from both speakers... In mono record, only left channel reacts which is correct.

Under the chassis is this slide switch. Moving the REC/PLAY switch moves this thing to make different contact. It's a bear to get out and I cleaned it 10 times.

When this happened, right channel was on then got softer and just went off and never came back.
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Schematic
Schematic
Owners manual hints
Owners manual hints
20250126_140117.jpg
Record meters
Record meters
Slide switch
Slide switch
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electra225
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Re: Fisher's Sony r2r

Post: # 24738Post electra225 »

Great explanation of the problem, Walter. I'm on my phone at work, so I need to wait until I get home on my desktop where I can see the schematic better. If the switch that is a bear to clean is after the VU meter, it would not be free of suspicion still. Your signal tracer may be very useful here....
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William
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Re: Fisher's Sony r2r

Post: # 24740Post William »

Looking at the Sony/Fisher I can were the 48 pounds comes in. Wow, that is a beast. I would agree with Electra 225 and the fact that you said after cleaning it 10 times it was better then went back to causing the problem.

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walyfd
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Re: Fisher's Sony r2r

Post: # 24745Post walyfd »

Every electrolytic was replaced. It worked for over a year then faded to black.

One thing I just thought of is recording something on it and playing it back on the Teac. I'd have to hook that up to the 500B but at least I'd know it records.

There's a coil on each channel that it looks like the meter is connected to. Could it be something like that?
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hermitcrab
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Re: Fisher's Sony r2r

Post: # 24763Post hermitcrab »

If you have a scope, it would be handy to trace the signal right from the heads, the switch looks like it has seen better days...inject a signal to the center post on the volume controls on each channel , then you could narrow it down ...
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Re: Fisher's Sony r2r

Post: # 24777Post walyfd »

Don't have a scope. Still looking at the diagram and marking things on the actual chassis.
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Re: Fisher's Sony r2r

Post: # 24820Post walyfd »

Looking at this area and specifically this choke:

I think it's somewhere in this circuit as this is "on" in playback but "off" in record.
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electra225
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Re: Fisher's Sony r2r

Post: # 24821Post electra225 »

That schematic is one that makes more sense when you can look at the device and the schematic at the same time. I'm not seeing exactly how it works. That choke is in one half of the 12AT7. What happens if you jumper that choke?
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walyfd
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Re: Fisher's Sony r2r

Post: # 24822Post walyfd »

Dunno. Haven't tried it yet but there's another one on channel 1 so what would cause one to fail yet the other always worked? A resistor? A cap?
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TC Chris
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Re: Fisher's Sony r2r

Post: # 24824Post TC Chris »

Is the choke there to keep the bias frequencies out of the output, where they can mess with FM stereo decoding?

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electra225
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Re: Fisher's Sony r2r

Post: # 24825Post electra225 »

As to why that choke could have failed. I don't know that a cap or resistor would necessarily be suspected of causing the choke to fail. You stated earlier that a dead channel was a known issue with this model. Maybe the choke is a high-failure item. You could replace the caps in the circuit, check resistors, maybe check the tube for a short. Jumpering the choke would let you know if it was the problem.
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