NOS pots...

[taliska]

Is there anything to be wary of when purchasing NOS pots? Could the tracks degrade over time?

Cheers,

Kaz

 

[JohnRoberts]

If they have been stored in a good environment I would expect them to be OK. Pots generally wear out from use, not degrade due to wiper oxidation from sitting over time, while that could happen in a bad (humid) environment. If you are talking about buying a significant number maybe buy one first and take it apart, I'd look for wiper oxidation or contamination on the resistive element, especially for non-hermetic sealed parts. Sealed parts are probably OK.

For less expensive non-sealed pots, it might be worth sacrificing one to determine the shape the entire lot is in.

JR

 

[thermionic]

The track lubricant in AB 'Mod pots' dries up over time. I've seen this in many examples. If they've been kept in a near-air tight environment they'll probably be ok, but they are very hit and miss in my experience. It's difficult to get new lube in there, although it can be done and makes them work like new. Once the lube's dried up they can feel and sound very scratchy. I've found this issue with different varieties of AB pot. I use ALPS pots that are 30+ yrs old all the time and they work like new. 

 

[taliska]

If they have been stored in a good environment I would expect them to be OK. Pots generally wear out from use, not degrade due to wiper oxidation from sitting over time, while that could happen in a bad (humid) environment. If you are talking about buying a significant number maybe buy one first and take it apart, I'd look for wiper oxidation or contamination on the resistive element, especially for non-hermetic sealed parts. Sealed parts are probably OK.

For less expensive non-sealed pots, it might be worth sacrificing one to determine the shape the entire lot is in.

JR

Thanks for the info JR. Yeah, these are sealed parts AFAIK. They're military spec pots like the vishay PRV6s, but made by a less well known manufacturer. They might not even be that old, haven't got around to asking that yet.

Haven't decided whether I'll go ahead and get them yet. Don't need as many of them as I would end up with, so only really makes sense to get them in order to help out the community, but the project I would be getting them for is on its last legs at the moment (specifically due to parts procurement I suspect), so need to check whether I'm just going to end up with a big box of pots I don't need...

The track lubricant in AB 'Mod pots' dries up over time. I've seen this in many examples. If they've been kept in a near-air tight environment they'll probably be ok, but they are very hit and miss in my experience. It's difficult to get new lube in there, although it can be done and makes them work like new. Once the lube's dried up they can feel and sound very scratchy. I've found this issue with different varieties of AB pot. I use ALPS pots that are 30+ yrs old all the time and they work like new. 

Ok, good to know. Everything I get tends to come from mouser or farnell, so this is a bit of an excursion in to the unknown for me. Thanks for the warning about the Allen-Bradley pots though...I'll remember to stick to ALPs ones if I venture further in to NOS territory...

Kaz

(The vishays I need are still available from RS, who accepted my order a couple of weeks ago, and then suddenly decided they could only fulfil a single item due to a manufacturing process change and line discontinuation. Now the back order date is mid-october, which is why I'm pursuing different avenues...well that and my slight annoyance...)

 

[thermionic]

If you're thinking of buying Sfernice pots (part of the Vishay monopoly), bear in mind that they feel as if the lube's dried out from the time they leave the factory. Horrible pots. Only use them if you can't get the taper / physical fit elsewhere. I recall Keith (or was it Geoff Tanner?) that Neve consoles destined for the Japanese market fitted Clarostat, as that market hated the Sfernice.

 

[lassoharp]

Like thermionic said.  The Allen-Bradleys don't come fresh off the virgin tree even though they are often priced as if they did.  I've found lots of erratic ones right out of box.

I've had some luck cleaning by drizzling cleaner down shaft while applying a very precise pressure on shaft - just enough to create an easier path for cleaner. Push in one direction and apply cleaner directly opposite.  Just be careful not to use too much force.  Sometimes it's very difficult and others it works fairly easy.  I've often had to repeat this process over a couple of days to let it fully seep in.  Like oiling a dried out Hammond organ.