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Old 13th October 2012, 11:02 PM   #1
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Default Scratchy pots

I recently bought a integrated amp and to my surprise the pots are not scratchy. Weird reason to start a thread but in my experience once a pot goes scratchy DeOxit works for a few months max before the evil comes back. Is there any way to prevent scratchy pots? This amp is about 30 years old.
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Old 13th October 2012, 11:29 PM   #2
bugeyed is offline bugeyed  United States
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Quote:
Originally Posted by Fredmullegun View Post
I recently bought a integrated amp and to my surprise the pots are not scratchy. Weird reason to start a thread but in my experience once a pot goes scratchy DeOxit works for a few months max before the evil comes back. Is there any way to prevent scratchy pots? This amp is about 30 years old.
Run them through their range 8 or 10 times once in a while.

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Old 14th October 2012, 05:26 AM   #3
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Worn pots are worn-out pots. The only way to restore the operation is to restore the worn carbon track which is a thin compound deposit on a round piece of insulating plastic.
That's not something easy or likely to be done on old equipment without identical spare parts from another pot, so a complete replacement is the only realistic option.
However, most DIYs work out that the light oil (diesel) in rust remover and water displacement sprays actually gives a temporary fix, as you also found. A longer lasting fix is by using a heavier lubricant and many pots were, if not still are supplied new, with a liberal coating of petroleum jelly aka "Vaseline" over the carbon track. This works great if the track is not too far gone and you can get access to the whole track either by the gap in the casing or disassembling it. Measure the track resistance and compare it with the marked value (out of circuit) to verify that it will be worth proceeding in the first place.

Sure, it's a hard way to service equipment but if you can't do it properly, then you have try any sensible way you can, right?
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Old 14th October 2012, 05:50 AM   #4
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Quote:
Originally Posted by Fredmullegun View Post
I recently bought a integrated amp and to my surprise the pots are not scratchy. Weird reason to start a thread but in my experience once a pot goes scratchy DeOxit works for a few months max before the evil comes back. Is there any way to prevent scratchy pots? This amp is about 30 years old.
Well, it will help a lot if the pot is sealed to prevent dust inside.
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Old 14th October 2012, 05:59 AM   #5
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i have tried butane lighter fluid, it works, also WD-40....
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Old 14th October 2012, 07:13 AM   #6
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Old 14th October 2012, 07:27 AM   #7
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I've never encountered a worn-out potentiometer. I've also never used Deoxit.

In my experience they can always be saved from the scratchiness. For a lot longer than a few months. Years, at least. And if it comes back, clean again.

Try other cleaners. Pure(ish) ethanol works wonders, for example.

Also don't try WD-40. It solidifies, and stops working - quickly. It's not good. Also, the gunk never disappears from the inside of the amp. You'll always have a disgusting, sticky, smelly amp.
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Old 14th October 2012, 08:43 AM   #8
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Originally Posted by Coconuts 500 View Post
Also don't try WD-40. It solidifies, and stops working - quickly. It's not good. Also, the gunk never disappears from the inside of the amp. You'll always have a disgusting, sticky, smelly amp.
'Used litres of the stuff, a little of it on electronics gear in emergency but never seen or heard of it solidifying. Hell, its 99% deodorised diesel fuel in butane propellant. Generally, you use such stuff with the supplied tube and drizzle it into the control, not all over the ship. Mind you, I've seen a lot of consumer equipment where someone has emptied the whole can inside, just as some idiots once sprayed their records, cassettes and player mechanisms with it.
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Old 14th October 2012, 12:40 PM   #9
DF96 is offline DF96  England
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I have always used Servisol Switch Cleaner. It is a solvent actually designed to do this job: cleaning off dirt and oxide layers. Surprisingly, it works. Unless the control is well past it, Switch Cleaner will usually keep it going for a few years before a further treatment is needed.

WD-40 is designed to be a water repellent and mechanical lubricant. I realise that many people use it on pots but I would not.
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Old 14th October 2012, 02:30 PM   #10
djoffe is offline djoffe  United States
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Certainly, pots can become scratchy if dirty or worn out. But they can also become scratchy if the adjacent coupling capacitor lets DC onto the pot by becoming leaky.

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