Scratchy pots

philflood · October 2009

I have a Crate CA-125 amp that is kind my my go to workhorse for any small gig or party. But, recently, the scratchiness of the main gain pot has gotten out of control. Some of the others are bad, too. Plus, this thing has 5 band graphic EQ that has always had it's share of scratchiness. I was able to open the thing up and parrtially disassemble it to get to the boards, but there is very little access of the pots. These are all mini pots, and there are about 20 of them. I am looking for recommendations on electronic cleaners that will improve the situation, and also any tips on the best technique to get the spray or whatever actually into the contact points. If there weren't so many, I would just consider rreplacing them, but with the number of pots in this amp, the repair value vs. replacement value does not justify the effort.

BettyBoo · October 2009

You need to spray some sort of alchohol based electrical lubricant into the pots. You can usually get something like this from a good hardware or electrical place - well thats the case down here at least. Just spray it into the pot (usually from the top or behind after you take the board out perhaps and just work it in by twisting the pot a few times, it generally wants to spread itself. Don't use anything that is silicone or kerosine based because they will attract more dust etc and will totally gum your pots up. It might sound crude but I also give pots/boards a hit of air from the air compressor too to blow out any dust, fluff, possums or any other crud so to speak. Works for me!

Hope this helps.

guitar3456 · October 2009

Try not to use alcohol based chem's as it might deteriorate the carbon or even the plastic insert shaft tabs. Try using DEOXIT if you need a chem cleaner and lubricant.

You can also turn the unit off and just spin the controls and and any slider pots at least a good dozen times. Just turn them kind of fast a bunch of times. That can usually knock the dust debris or bad spots off the wipers (in the pots).

Manitou · October 2009

Deoxit at Stewart-MacDonald >> http://tinyurl.com/2hn6p5
I would first run the pot through it's full range a number of times, with the amp off. If that doesn't work, you will have to use the Deoxit cleaner.
There will be a couple small square holes on the pot to work the spray. Or you can try introducing the cleaner at the base of the shaft.
If the problem keeps coming back, you have to replace the pot.

The contacts get dust and even corrosion, (after the protective coating on the contacts wears away) and this is what causes them to get scratchy.
If they have more than moderate use, and age, they could be worn out, and dust or corrosion builds up on them quicker.

Side note;
Cost of new mini-pots are about $2.75 each, so you are right, this is a chunk of change. (x17... I downloaded the manual at Crate.com)
The EQ is a slide version pot. Cleaned the same way.
Consider the cost of the cleaner, and if you know these pots to be old and well used.

philflood · October 2009

Thanks, guys. I'll get some Deoxit and give it a shot. The pots do appear to have a verry small hard to get at access hole, but I believe I can get the spray tube into them.

Manitou · October 2009

\philflood\ wrote:

The pots do appear to have a very small hard to get at access hole, but I believe I can get the spray tube into them.

Working the spray at the shaft will work if you have some too difficult to get to. StewMac sells a pot cap. http://www.stewmac.com/shopby/product/0291
(hint; you can click on stewmac photos to enlarge them)
They are pricey, but work on pots difficult to clean otherwise. You're not trying to protect a guitar finish, so you probably won't need this. But you could maybe make one easy enough, if you want.
After you spray, work the pot full range a bunch of times, and let dry before you put power to them, to check them out. Best of luck to you. 8)

gtaus · October 2009

Always try turning the knobs full range a number of times to see if that improves your scratchy pots. If not, I have found that our local Radio Shack sells a tuner cleaner that has always worked well for me. http://radioshack.com/product/index.jsp?productId=2103700. I don't know how it compares to Deoxit, but the Radio Shack tuner cleaner is a little bit cheaper ($10.99) and for me, available locally on the store shelf, and has worked well everytime I needed it. My can came with a small straw to spray into the smallest spaces.

Having said that the tuner cleaner always worked great for me, I must also state a disclaimer that I have had some old pots (30+ years old) that I just could not clean no matter what I tried. Sometimes the only solution is replacement. Best wishes.

Scratchy pots

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