Quieting Old Pots on Pioneers that dont quiet down--Suggestion

stereofisher

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As posted earlier I have acquired a small QX 4000 Pioneer Receiver off the 'Bay for $26 with shipping. Fixed her up. Needed dial lights from Bob at Vingtage. It also needed a dial pointer light that I robbed off an parts QX 8000. The seller didn't mention it had a broken AM antenna holder. Also robbed from the 8000 parts unit. After a good cleaning. It works well on AM,FM and all inputs. Its cabinet was broken on the upper right hand corner and I was successful reglueing it with no gaps is the jounts. :banana: It looks good. Used wood filler to the fill in the upper back corner that was broken out. Came out nice :thmbsp:

Now the problem. This receiver is working well. Cleaned the pots. Like a SX 1000 TA receiver, it must have been in a damp area. Two of the pots did not respond to cleaning with Deoxit. The bass and one of the balance controls are very noisey and would not quiet down :thumbsdn: The bass is the worst of the two. Useful only when its turned up full or at the flat setting. Static is deafining. The controls are soldered to the circuit board and nearly impossible to get at. Other than replacing the controls anyone got any suggestions? Not the I plan on using the reciever. Leave it alone and it makes a good test reciever to work on turntables,tape decks and anything that makes noise. Would like to use her in the guest room. Could get by not resetting the controls. Hope some of you folks out there can help.

Thanks in advance. Eric
 
If there is DC on the pot, no chemical on Earth will help. There are problems on the board that need to be addressed.
 
Where do you check for DC on the Control?

EchoWars said:
If there is DC on the pot, no chemical on Earth will help. There are problems on the board that need to be addressed.

I have the service manual for the bigger 8000. The control is quiet on the center setting and full bass. Plays well on these settings. Noisy else where. What do I need to do to check for this problem? Do I check at the controls? The 4000 plays well other wise.

Eric :thmbsp:
 
Look at the schematic in the area of the tone controls. You should see a coupling cap on the input side of the control and probably another on the output. With a voltmeter, probe the 3 terminals of the control on each section of the control. You should have 0 volts (to ground) if the caps are good. If you have voltage, replace the caps on the input and output side of the control, both channels. That should fix it. Also check the same thing on the volume control.
 
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