How bad did I screw it up??? - diyAudio
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Old 11th July 2008, 04:29 AM   #1
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Unhappy How bad did I screw it up???

I looked over sub forum descriptions and didn't see a better place to post this, so here goes.

I have a Carvin SX-200. Was working pretty good except for some scratchyness in the volume pots. And a loud hum when the effects level was turned up. So a friend said I could spray maf cleaner in the pots and likely clear some of the noise up. maf=mass air flow which is a sensor used in cars. Maf cleaner is nothing but an electronics cleaner. A very quickly evaporating liquid.

I went to the local auto parts store and instead picked up brake cleaner. Which is basically the same thing but for, you guessed it, brakes. Very quick drying liquid in an aerosol can that leaves no residue.

Anyway, I generously sprayed all the pots. Working the knobs to the stops, I sprayed it into the small hole in the pot's casing. Gave it plenty of time to dry. It's been 24 hours now. Plugged everything back in and it sounds horrible.

Usually, I could put the volume knob on 1 on a scale of 1-10 and that would be plenty loud. Now I need to turn it up to 4 or 5 to get too much sound. And it comes and goes. It can be low and then super loud. Very random. It almost sounds like the speakers are blown because the sound is so distorted. Once in a while I can pluck a single string and get a good solid clean tone. Most times it doesn't though.

Changing bass, mid, treble, overdrive, or presence does not change it(changes each of their functions, not the quality). Changing channels does not help. Changing cords does not help. Changing inputs doesn't help.

I took out the board that all the pots are on and looked for obvious damage and could find none. Nothing looks melted or burned up. All solder connections look fine. Can't see anything loose.

Please help. I miss playing.
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Old 11th July 2008, 05:50 AM   #2
MadMutt is offline MadMutt  Australia
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Time for new pots.

You stuffed them.
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Old 11th July 2008, 07:04 AM   #3
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Woohooo!

I fixed it. I took it apart and just stared it while I was thinking, "what the heck could have this cleaner done to screw it up?"

Apparently several of the pots had been replaced before. The solder they used was a little heavy in the flux department. The brake cleaner dissolved the flux and it ran onto different terminals effectively causing a short circuit. I cleaned all of it up with more of the cleaner and cue tips and it sounds awesome. Even got rid of the hum I set out to get rid of in the first place.
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Old 11th July 2008, 10:10 AM   #4
Nordic is offline Nordic  South Africa
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Flux is a lady dog on old equipment... even just overhauling my old 1978 Big Muf Pi deal I noticed a big drop in noise after just cleaning the board of big gobs of flux... after replaceing the 4558 chip it is now even more quiet and happily alive in the 21st century
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Old 11th July 2008, 10:26 AM   #5
AndrewT is offline AndrewT  Scotland
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I was about to jump in and say "brake cleaner, serves you right", but it seems you have hit upon an excellent way to clean old uncleaned PCBs.

Can anyone else say why brake cleaner should not be used?
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regards Andrew T.
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Old 11th July 2008, 11:03 AM   #6
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Some brands can be bad for plastics and rubber.
I just looked at the can of CRC "Brakeleen" I have on the shelf,and it warns against using it on plastic and rubber parts.

It does evaporate fast,and leaves no residue...but it just doesn't seem like a good idea to me? I dunno.
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Old 11th July 2008, 12:14 PM   #7
MadMutt is offline MadMutt  Australia
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Congrats.
I was expecting it to have disolved the carbon off from the pot tracks.

I'm glad for your sake it was much less dramatic...
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