help me trouble shoot - guitar amp crackle

Hi...

Clean the control with a little bit of electronic control cleaner.

Not even necessary to disassemble the unit. Buy a spray can of cleaner. Unplug the unit, remove the knob, rest it on its back so that the control shaft is pointing up. Spray a quick burst or two around "bearing"; where the shaft turns. quickly rotate the control from low to high position back and forth a dozen times. Give it another quick shot, rotate again. Let it dry thoroughly and it "should" be good as new.

Take care.

Ken

if you really mean TOUCHING it without moving creates noise, then it may be a bad ground...

the case of the control and therefore the knob should be grounded to the chassis

Mark

If you feel comfortable opening up the amp, and are aware of the safety precautions required:

Firstly, check the pot's soldering is sound. If it is-

Get a can of *lubricating* switch cleaner with a nozzle tube from an electronics shop, locate the pot inside the amp and try to find an opening in the pot, usually above the pot's terminals. Fit the tube to the can nozzle, insert it into the opening and spraya small quantity of fluid in. A brief burst is sufficient. Work the pot back and forth to spread the fluid around.

Power the amp up and test the pot. If the problem remains, repeat until it clears. If still no joy, you'll maybe have to replace the pot. In some cases dismantling the pot and cleaning the resistive trace and contacts with swabs works well, but that entails desoldering it, bending back the retaining lugs and seperating the resistive element from the metal body. Not really a job for a novice, but it's not that difficult.

I would avoid the temptation to try and spray the fluid in by taking off the knob and spraying it through the front. It will take a lot of fluid to eventually get along the shaft into the pot, most of it will be wasted and just make a mess!

Also, that nice, smooth drag effect most pots have will be completely destroyed by squirting cleaner along the shaft- the effect is caused by a heavy, viscous oil between the shaft and bearing which will be washed away by the switch cleaner. You'll end up with a slack, easy to turn pot (and hence easily accidentally knocked off its intended setting!) possibly with a rough or inconsistant feel to it.

Also, you could end up with a mix of switchlube and viscous damping oil in your pot. The lube solvent will evaporate leaving a nasty, non-conductive mess which could make things even worse.

You'll also destroy the viscous damping effect by spraying too much switchlube in the back as well, as it will seep into the space between shaft and body. Take care to spray very small amounts between tests.

Good luck.

Dave

Pot problem. To do it without spending a cent, use a medicine dropper, suck rubbing alcohol and place a few drops into the pot. The pot's terminal should be upwards, then turn pot all the way both directions a few times. You may also try WD40 or any contact cleaner available - don't buy - otherwise, just buy a new pot. Bobby

Whilst the foregoing advice may well be correct there is another possible reason. In older amps that used electrolytic coupling capacitors, it is common for those capacitors to become "leaky" which means that DC will be appearing across the pot. The only cure is to replace the faulty capacitors.

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Regards ......... Rheilly Phoull

Dave's comprehensive treatise hits the 'pot! :-)

I'd just caution that rather than use WD-40 (as one other poster recommends), use 'Servisol Super 10' - if it's available to you - as it does not leave loads of dust-gathering oil residues for evermore! Stressing the get-at-it-from-the-back tip; most panel-mounted pots with metal cases have those two crimped indents to support the track assembly inside. One of these is the ideal place to point the Servisol pipe into. With servisol, you don't need to be too worried about overdosing the pot with lubricant - most of it seems to be ("CFC-free?" :-O ) cleaner - but it *is* flammable, so pay attention to safety directions on the can!

I recently 'restored' several pots on my 28-year-old Carlsbro amp using this material/method. The results were so good, I sold it in no time!! :-/

** BE SURE TO REMOVE MAINS CONNECTION to your amp before removing any panels/components!! **

If this fails, I think Dave has said the rest! :-)

Cheers,

+ ++Pete.

Never never ever use WD40 on electronic equipment - this topic has been gone through hundreds of times in various newsgroups as to why not, even the manufacturers of WD40 dont recommend it.

Ron(UK)

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