Marshall guitar amp pots cleaning

Thread Starter

atomtm

Joined Aug 13, 2012
24
Hello!
I have some trouble with my Marshall Valvestate (VS15r) and to be more specific with it's potentiometers . When I turn the gain pots , i get scratching sounds or no sound at all !
It seems there is a lot of dirt inside them so I was wondering if there is a safe way to clean them (Contact cleaner?) . I ve seen videos cleaning guitar amp pots , but they are not of my type . I have attached what mine looks like.
Is anybody familiar with this guitar amp , and if so could you give me a guideline on how to clean them or with what pots to replace them?

Thank you in advance



2.png 3.png 1.png
 

ian field

Joined Oct 27, 2012
6,536
Hello!
I have some trouble with my Marshall Valvestate (VS15r) and to be more specific with it's potentiometers . When I turn the gain pots , i get scratching sounds or no sound at all !
It seems there is a lot of dirt inside them so I was wondering if there is a safe way to clean them (Contact cleaner?) . I ve seen videos cleaning guitar amp pots , but they are not of my type . I have attached what mine looks like.
Is anybody familiar with this guitar amp , and if so could you give me a guideline on how to clean them or with what pots to replace them?

Thank you in advance



View attachment 78185 View attachment 78186 View attachment 78187
Be wary of using switch cleaner spray - many components of this type have ABS plastics in their construction - it can fail spectacularly in contact with hydrocarbon solvent/lubricant.

In my TV repair days, I remember spraying a VCR mode switch with switch cleaner - I watched in amazement as the plastic snail cam turned into tiny granules in front of my eyes!

If you have the patience to carefully disassemble the pots and put them back together, an old trick is to polish the carbon track with a pencil - use a HB pencil (softer graphite - less clay).
 

cmartinez

Joined Jan 17, 2007
8,218

MrChips

Joined Oct 2, 2009
30,707
I'd simply go ahead and buy them new... in my experience, cleaned pots don't last for too long before they need maintenance again
I believe I haven't found a carbon volume control pot that does not eventually run into this problem. So you can either keep replacing the pot after every so many years or squirt contact cleaner every so many years.
 

Lectraplayer

Joined Jan 2, 2015
123
You can try contact cleaner, and it probably will help big time, but I have also had luck with that PTFE oil Radioshack used to have. Some type of grease like that will also help. Other than that, you may have to replace the pot
 

#12

Joined Nov 30, 2010
18,224
Sad, but true. I have some 1K wire wound pots from 1973 that are so good that I try to use them in new designs.
Carbon pots? Can't get ten years out of them without maintenance. :(
 

cmartinez

Joined Jan 17, 2007
8,218
I believe I haven't found a carbon volume control pot that does not eventually run into this problem. So you can either keep replacing the pot after every so many years or squirt contact cleaner every so many years.
I'd correct that last sentence to "So you can either keep replacing the pot after every so many years or squirt contact cleaner every so many weeks"
 

ian field

Joined Oct 27, 2012
6,536
Funny, but not true. My 1977 Onkyo audio amplifier is ready for its third squirt job at 38 years old.
Depends on the quality of the pot - in some; the carbon track is washed off by solvents in the switch cleaner, then the effect lasts forever.
 

#12

Joined Nov 30, 2010
18,224
Stupid me... I got confused and thought we were talking about an electric guitar... I was speaking from personal experience
I have to give you the point on this one.
Besides, 1977 carbon pots had not been, "improved" to today's standards. :rolleyes:
 

Thread Starter

atomtm

Joined Aug 13, 2012
24
Seems it's out of production!
Customer services didn't give products catalogue or something similar .
Anything else I can do to find what potentiometers I have to buy?
There is a label (shown also at the pictures I have attached ) , b200k . Would that mean 200kohm logarithmic?
 

ian field

Joined Oct 27, 2012
6,536
A while back I acquired a Fender practice amp, unfortunately the previous owner hadn't treated it well - I was looking into buying replacement pots, and getting well into the realisation that it would be cheaper to buy another s/hand amp, when on the way to visit a relative, I found an amp just laying under the hedge alongside the footpath. Not as good as the fender could have been and even google had never heard of that brand, but all it needed was a squirt of switch cleaner on the input jack.
 
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