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The 12-position 4-decked rotary switch on this Roland Re-201 dating back to the '70s or the '80s is completely stuck and won't move at all due to corrosion. The wafers on it's decks seem phenolic.
The contacts can't be easily reached, with about 1 mm of gap between each deck. I have tried a contact cleaning spray, and WD-40. Nothing worked. The switch just would not turn. How do I make it turn?
It looks like you should be able to totally disassemble the switch by removing the 2 nuts holding all the wafers together.
There is a recent episode of 'CuriousMarc' on YouTube where he does the same thing, at about 8 minutes 30 seconds into the video.
In his case, the old grease on the shaft has solidified. He managed to disassemble it, re-grease it and put it back together.
If it's corroded there is no way to restore it… your best bet would be to find some kind of replacement. You could try an heroic restoration opening the switch pack (usually they are riveted)
As has been suggested, removing the nuts should allow the wafers to be separated. These multi-pole wafer switches have an indexing mechanism at the shaft end, and this should allow you to access that to free it if necessary. You will also get access to the individual contact wipers on the wafers - if these have corroded and become fixed then I would definitely look for replacements. Vintage wafer switch assemblies are available on sites such as Ebay.
Had a similar situation with a rotary input selector on a vintage 1970's Harmon-Kardon tuner/amp. Soaking it with 99% pure isopropyl alcohol helped a bit. Then applied mineral oil using a needle applicator and let it sit overnight. A second application of mineral oil the next day did the trick. Cleaned the switch again with isopropyl alcohol to remove excess oil, then finished with a spray contact cleaner.
