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Fisher RS-1080 channel imbalance

Franco989

Franco989

Member
Hi Everyone,

Got my first Fisher (traded a turntable for this beast) and it has some issues. The right channel is lower than the left, from my perspective the left channel is where the volume should be (at 170 watts the volume knobs is usually puts out alot of power without turning it up to much, atleast that's my experience with my pioneer sx-1050 ). Used different speakers, same issue, have also deoxit all knobs and switches but this didn't help. Any one have have any ideas I could try? Thanks
 
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If this unit has pre-out, main-in jumpers, remove them. If the unit used a switch to connect preamps to main amps, make sure to clean and deoxit this switch as it can be a problem
Use a pair of audio cables and plug the plugs on one end to the pre-out connectors. Put the volume at a fairly low level. Use one of the loose RCA plugs and plug into the main -in left, remove, and plug into the main in right. If you notice a drastically different volume level, then the problem is in the Right Driver/power amp section. If the volume level is the same, then the problem is before the Driver/output section, in the switches, or preamps or tone amps. To verify just use the audio jumpers and use the plug from the left pre amp out to feed the right main map, and use the plug from the right preamp out to feed the left main amp in. Test the unit and you should have good volume on the right side, and low volume on the left side.
If the problem is pointing to the driver outputs, reinstall the original jumpers, and try tapping on the speaker protect relay. If the volume pops up and down, the relay is dirty. You can try cleaning, but it may make sense to just replace it, if you are not familiar with cleaning relay contacts.

Of course you should test the unit fully, and make sure that this low right channel is found with FM, and AM, and phono, and tape monitor.

Of course it could always be bad components, or bad connections, but try the test swapping left and right main amps being fed from the same side on the preamp (left or right.), and then feed from the left out to right in, and right out to left in, to isolate and confirm where the problem is.
 
Tom B said:
If this unit has pre-out, main-in jumpers, remove them. If the unit used a switch to connect preamps to main amps, make sure to clean and deoxit this switch as it can be a problem
Use a pair of audio cables and plug the plugs on one end to the pre-out connectors. Put the volume at a fairly low level. Use one of the loose RCA plugs and plug into the main -in left, remove, and plug into the main in right. If you notice a drastically different volume level, then the problem is in the Right Driver/power amp section. If the volume level is the same, then the problem is before the Driver/output section, in the switches, or preamps or tone amps. To verify just use the audio jumpers and use the plug from the left pre amp out to feed the right main map, and use the plug from the right preamp out to feed the left main amp in. Test the unit and you should have good volume on the right side, and low volume on the left side.
If the problem is pointing to the driver outputs, reinstall the original jumpers, and try tapping on the speaker protect relay. If the volume pops up and down, the relay is dirty. You can try cleaning, but it may make sense to just replace it, if you are not familiar with cleaning relay contacts.

Of course you should test the unit fully, and make sure that this low right channel is found with FM, and AM, and phono, and tape monitor.

Of course it could always be bad components, or bad connections, but try the test swapping left and right main amps being fed from the same side on the preamp (left or right.), and then feed from the left out to right in, and right out to left in, to isolate and confirm where the problem is.
Click to expand...


Thanks for your suggestion, I tried what you suggested with RCA cables but didn't notice a difference in the sound and the problem stayed isolated to the same channel. I also tried tapping on the relay but this didn't cause the volume to jump up and down. I have a feeling the power amp section is working accordingly. Would you think the problem might be in the pre-amp board?
 
Have you cleaned any of the pots and switches 1st. This is recommended to do 1st to rule out dirty contacts. Tape monitor, low and high filter switches and such are notorious for this problem especially in 60's and 70's gear. Clean with DeOxit D-5 and follow up with Faderlube F-5. Exercise the switches and pots after spraying about 50 cycles.

If you have another amp/receiver with the jumpers you can cross connect them and test the preamp separately from the amp. PRE-OUT on the 1080 to MAIN IN on the other amp. Test. Then PRE-OUT on the other amp/receiver to the MAIN IN on the 1080.

This will tell you whether the problem is in the AMP or Preamp sections.
 
So here is something interesting. For some magical reason both channels started working properly this morning. After testing the receiver for a couple of hours I decided that it was working accordingly and was going to put it back together. I sprayed some deoxit on the Function & Speaker potentiometers and and put the bottom plate cover on. I turned it over and with the bottom plate up started putting back all the screws. After I was finished I decided to test it again, I'm not getting any sound now. :confused: I have turned the volume way up to hear a faint sound coming from the speakers inputs still function it's just the sound thats really low. I'm guessing it has to do with the amp, but not sure how to proceed from there. BTW I do hear the second relay click so I know this is working.
 
Never-mind, I know the amplifier works because I just connected an audio source directly to it and I got the correct amount of sound from the speakers. Still wondering what the heck happened and why I'm getting a very faint sound when I connect back the jumpers.
 
Like not being able to find your a** with both hands, in a lit room and a 10 man working party handy. Been accused of that a few times.
 
Hello I have the Fisher RS-1080 and have the manual and dc offset is good but I’m not understanding the idle current measured across the R22 I’m use to Hafler’s removing the fuse and then make the adjustment with the meter in amps setting across the open fuse
Please chim in with a better explanation
 
According to the manual I got off HIFIENGINE, you read across R-14, not R22. (One probe on one end of the resistor, and the other probe on the remaining end of the resistor). Measure voltage drop which should be 0.038v Plus or Minus 0.001v
rs-1080 bias adjust.jpg
 
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Yeah, at 1st I thought so too, but wmeyer(post 12) also posted on the other thread I linked to in post 14.
 
R22 threw me for ages .. i first thought R37 even before i saw the schematic . across an outputs emitter resistor is obviously the way .
 
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