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Question for technicians

Recently I noticed my system was sounding dull and flat. Then I discovered there was little to no sound out of the right speaker, just an intermittent weak signal accompanied by static. Later, I noticed that I could make the signal come and go by merely touching the preamp's input selector switch, or applying a slight push-or-pull pressure to the control knob. I don't have any audio shops around here that I trust and I can do simple things like solder touch-up, continuity checks with a vom etc... Any ideas of how to go about checking this out? (greatly appreciate any and all advice)
rawinsonde
atmasphere's avatar
atmasphere
12,039 posts
 
If you can't get to the switch itself then the cleaner is likely not going to do the job by trying to get it to go through the shaft bushing for the switch!

Your best option at this point is actually pretty simple- operate the switch vigorously to both limits about 50 times and see if it gives you any trouble after that. The only reason its a problem is corrosion from lack of operations.
rawinsonde OP
47 posts
 
Just for the record, I believe I said "selector" switch in an earlier post, but the faulty switch is actually the balance control (L to R) ... I'll try Atmasphere's vigorous attack method as that stuff seems to dry instantly and I doubt that it has any penetrating ability.
atmasphere's avatar
atmasphere
12,039 posts
 
I work on vintage electronics a lot. The better stuff frequently have 'J pots' in them- Allen Bradley J-Style potentiometers. They are really well sealed. If they get noisy, the technique above actually works fairly well on them unless they are really far gone. In that case you have to drill a small hole in them which is really dicy, but at least then you can clean them.
rawinsonde OP
47 posts
 
this is an arc sp9-ii if you happen to know what style pots it has... I worked the switch many times as you suggested and it appears fine. hope it holds up. thanks
rawinsonde OP
47 posts
 
Twice I have rotated the bal switch end to end maybe 50 times. It works for quite a while and then you do it again. I guess the friction burnishes the contacts enought to eliminate the oxidation and make a good contact. In due time, the cycle repeats.... thanks to all of you who contributed to the issue!
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