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Fredmullegun 13th October 2012 10:02 PM

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.

bugeyed 13th October 2012 10:29 PM

Quote:

Originally Posted by Fredmullegun (Post 3200462)
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.

Cheers,
kev

Ian Finch 14th October 2012 04:26 AM

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?

lanchile 14th October 2012 04:50 AM

Quote:

Originally Posted by Fredmullegun (Post 3200462)
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.;)

AJT 14th October 2012 04:59 AM

i have tried butane lighter fluid, it works, also WD-40....

Cal Weldon 14th October 2012 06:13 AM

WD-40 :checked:

Coconuts 500 14th October 2012 06:27 AM

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.

Ian Finch 14th October 2012 07:43 AM

Quote:

Originally Posted by Coconuts 500 (Post 3200810)
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. :eek:

DF96 14th October 2012 11:40 AM

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.

djoffe 14th October 2012 01:30 PM

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.

Update My Dynaco

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