Advice on cleaning rotary encoders and potentiometers on a scope

[killingtime]

Hello,

Anyone on here have experience cleaning up switch contacts and potentiometers?

I have an old Hameg 204 CRT scope. It works - sort of - if you tap and wiggle the rotary controls. It's 80's vintage and the rotary encoders exhibit intermittent contact. Some of the pot controls need a wiggle before the wave form settles down.

There are many threads on this, on many boards, but my questions are specific to this scope:

1. How do you get the contact cleaner into the pots - they're metal and sealed?
2. How do you get the contact cleaner into the rotary encoders - there' s no access to contacts?

Here's a picture showing the encoders and pots.

There's a wealth of info around this on audio forums. Some suggest drilling a hole in the pot (upwards, so any metal chips fall down away from the pot) and squirt cleaner in. I can't take the pot apart as it's riveted together and made of metal. I suppose I could just replace them with an equivalent.

Then there's the rotary encoders. Timebase pictured, they're a work of mechanical art, and the contacts are flanked by plastic. I read somewhere you're not supposed to get contact cleaner on plastic parts - which rules out drilling a hole and squirting cleaner in..Depends on the cleaner I suppose.

The original plan was to drill some holes and hose everything down in contact cleaner, but after a bit of research this seems to be a bad idea. Some switch cleaners attack plastic. I've read many times on audio boards that a targeted approach is the way to go. Use 'switch contact cleaner' on the actual metal contacts only, and potentiometer cleaner on the pot tracks. A common mistake is to use too much cleaner which then also removes grease in other areas.

I really don't want to desolder the rotary encoders. That's  a car crash waiting to happen. Broken / lifted PCB tracks etc.

I was going to use 'Servisol Super 10' on the mechanical switches and ' Kontakt PR Potentiometer Cleaning Spray' on the pots. Other posts suggest using a liberal amount of IPA although but you'd have to remove the switch/pot from the PCB for this to work.

Any ideas?

Thanks.

[bob91343]

I wouldn't mess with it.  The cause of the wonkiness is probably lack of use.  Exercise the pots and switches and they are likely to fix themselves.