Anyone out there that has vintage audio equipment can utilize this method on open-frame switches whether the switch components are silver or bare copper and/or brass. Abrasives can work with limitations, but not recommended. You do not want to damage the fit-and-finish of a viable switch.
My McIntosh MR-67 FM tuner developed a problem where the left channel became much lower in level and distorted. To make a long story short -- it turned out to be a corroded mode switch (heavy silver oxide) that passed both the mono output to the audio output stages from the ratio detector (one switch position) or stereo output (second switch position) from the multiplex board. To add insult to injury -- the switch was no longer available -- no vendor had any of these 50-year-old switches sitting on a shelf looking for a home.
As it turns out the switch looked worse than it appeared, but a solvent-based contact cleaner could not get the job done. Hell – it barely mattered. So – if that didn’t work – what will?
TarnX (an aggressive liquid silver-cleaner) from my well-equipped kitchen together with a moderately stiff utility brush stripped the corrosion (silver oxide) down to some beautiful virgin silver. I used the contact cleaner to flush away the TarnX as remaining TarnX residue will enable corrosion to occur again – then I treated the switch with CAIG DeoxIT to prevent oxidation.
It is important to note that the chassis area near the work site should be layered with some paper toweling to soak up the TarnX during that phase of the cleaning. I kept the paper towel in place even during the contact cleaner flushing. Compressed air keeps things neat and tidy.
I didn't think to photograph the switch before cleaning -- but you can see from the attached photo the restored switch is as good as new.
I hope this helps.
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MR67 Mode Switch.JPG [ 340.12 KiB | Viewed 15258 times ] |
