Dirty dial switches on a Metra Blansko L110 decade box

[onesixright]

Hey Guys,

I got a old L110 decade resistor box (Czech made, Metra Blansko). I looks good, but unfortunately the rotary dials are, i think, pretty dirty. I opened the box, but each decade is soldered against the other. Anyone has a amazing trick how to clean the each switch (easily)?

daqq did a peak inside the box, https://www.eevblog.com/forum/metrology/metra-blansko-resistance-decade-peek-inside-)/

I measured the output (4 wire), its often wrong. If you just wiggle the dial a bit it gets better, but great its not.

I could only think of desoldering each decade (and hope I can access the switch), it seems just one solder joint. But im not sure if its wise to do.

See the pictures, Thanks!

[SeanB]

how about some contact cleaner down the front opening where the thumbwheels is, on the side where the board is, followed by a shot in the rear side with the front down, and then run each switch a few times through a few revolutions while wet. That should clean them up a lot and get better contact repeatability.

[onesixright]

Thanks!

Well my problem with that approach was, shouldn't you dry/clean the contact fluid? Or can you just let it vaporise  ?

If the latter its worth a try...

[SeanB]

It will evaporate off naturally, no need to dry it, just use enough so the dirt is washed out of the contact area.

[Smith]

Normally I would use IPA. But because of the printed dials I would be careful with IPA because it can harm the paint on the dials. IF you can disassemble the encoders (some can easily be disassembled, some do not.) you could just clean the contacts with some simple erasers.

If you are using a strong contact cleaner it might be a good idea to wash it off with some distilled water and let it dry thoroughly. Contact cleaner can really hurt contacts in the long run.