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Sony CFS-1000S balance/eq problem


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#1 Reaper83

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Posted 04 September 2017 - 10:55 PM

I just got a Sony CFS-1000S in really good condition.  All functions work great.  The only issue I have is that the right speaker is louder than the left on all sources, including the radio.  I even put FM in mono and it's less noticeable but the problem is still there.

 

I tried the obvious by switching speakers but then the other speaker was lower when plugged into the left channel.  I disassembled and cleaned the sliding balance and volume controls but it didn't help.  Through trial and error I have it narrowed down to the equalizer.  If I put all 5 bands in the -10 position at the bottom, both speakers have equal volume.  When raising the equalizer the right channel is boosted more than the left, especially when increasing the 10kHz slider.  It increases the treble of the right channel, but mostly just increases background static and tape hiss in the left channel. 

 

I disassembled the 5 slider switches and cleaned them.  I also re-flowed all solder points on the eq/volume board, including the 5 switches and the IC which controls the eq.  I also re-flowed the power amp IC on the main board.  At this point I have nothing left to try but start blindly replacing components, which I'm not doing.  I don't have any experience repairing boomboxes and I have no idea where to go from here.  Nothing looks burnt or damaged that I can tell.  Does anyone know of any specific components which would cause this problem, or is it just not repairable?

 

If it's any help the service manual is available at http://freeservicema...y/cfs-1000l.pdf

 

It's for a CFS-1000L, but the only difference is my model has shortwave.  Most of the components are the same by the look of the schematics.



#2 ralrein1

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Posted 04 September 2017 - 11:54 PM

Try spraying a goodly amount of Deoxit D5 in the record bar. Then work it back and forth about 60 or more times.Also spray the headphone jack and then plug in and out a set of headphones many times. I hope this helps you out.

#3 Reaper83

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Posted 05 September 2017 - 07:14 AM

All I have is contact cleaner.  That should help too I guess. I haven't had any trouble with it on plastics before.  This happens on all sources, would the tape record bar affect everything else as well?



#4 Reaper83

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Posted 05 September 2017 - 12:54 PM

I just finished cleaning everything up.  I put the board in a vertical position and squirted contact cleaner into the record bar, while moving it back and forth.  I did the same with the tape/radio switch and the tuner band switch.  I also cleaned up the speaker terminals, the headphone jack, and both rear mic inputs.  I dried everything up with compressed air and tried it again.  Still no difference.

 

The right channel is louder than the left unless the equalizer switches are all at -10.  Maybe it's not the equalizer, maybe it's just more noticeable when the sound is boosted.  At this point I have no idea what to do with it.  Maybe a capacitor or other component is failing, but I have no way to test it and I don't even know which ones would control the speaker balance/volume.  Maybe the boombox is just old and worn.