a crate combo amp for guitar.
touching the "high" pot (3-band EQ, low mid high pots) makes a loud
crackle right thru the power amp section and out the speaker
turning the pot, touching it lightly, tapping on it - same result -
loud nasty sound
touching any other controls or chassis, no problems. even shaking the
amp, no problem.
it's only touching or turning the one pot.
does this sound like a simple solder or inexpensive pot replacement??
thanks!
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
