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Potentiometer Refurbishment


Hutton
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I've taken pots apart before now, and 9 times out of 10 any repair work is very short-lived. The only time I'd recommend it is making up your own dual-ganged pots, where you need two different values/tapers on the same shaft.

Buy some high quality pots and replace the old ones. Personally, I'd rather have a functional bass than be simply holding it for the next buyer.

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It seems to me that you just need to find a 1981 pot and replace the replacement. The soldered joint has already been broken so no additional damage to the "originality" can be done here. That's the best you can do.

There are various levels of OCD when it comes to collecting vintage things. The guys who will pay the most will demand the highest levels of originality and condition, and why not?

If you have a busted bass or one that has a serious problem you've got to fix it. You'll get nothing for a non-runner, so you fix it and move to the next level of vintage collecting. The almost original level.

IMO, a replacement pot shouldn't be a deal breaker. As far as I can see very few people would have a problem with a date-correct replacement.

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[quote name='Meddle' timestamp='1456011890' post='2984588']I unpicked the tabs that hold the pot together, cleaned the carbon track with an eraser and reassembled the pot.[/quote]

A variation that dates back to steam radio days. You can coax extra life out of an old pot by using the tip of a pencil to clean the track. The graphite is hard enough to dislodge any crusty stuff and slippery enough so as not to gouge the surface of the track. It also leaves a fine coating of graphite as dry lubrication. If you're patient and careful, it beats spraying.

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I'm about to do something similar on my 79 P. I'm replacing pickups, pots, cap and jack; and keeping the originals joined together with their original solder and wire for provenance. All that is lost is the original connection to the bridge ground wire.

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[quote name='Kevsy71' timestamp='1456352609' post='2988296']
I'm about to do something similar on my 79 P. I'm replacing pickups, pots, cap and jack; and keeping the originals joined together with their original solder and wire for provenance. All that is lost is the original connection to the bridge ground wire.
[/quote]

If I was doing that I'd put in a new bridge earthing wire. Is the original even soldered to the bridge plate or just trapped between it and the body?

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[quote name='BigRedX' timestamp='1456428576' post='2988999']
If I was doing that I'd put in a new bridge earthing wire. Is the original even soldered to the bridge plate or just trapped between it and the body?
[/quote]

In defence of unsoldered bridge wires, it's not cost effective (or necessary) to solder to the bridge, as it's an enormous heat-sink, and you'll be at it for hours!

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[quote name='BigRedX' timestamp='1456428576' post='2988999']
If I was doing that I'd put in a new bridge earthing wire. Is the original even soldered to the bridge plate or just trapped between it and the body?
[/quote]

The bridge ground wire is in pretty good nick so I was just going to solder the end to the new volume pot. There was no buzzing before so I assume there is contact with the bridge (in fact where they even soldered originally)?

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In the interests of keeping the original loom intact, I'd leave the earth wire attached and check how it is attached at the bridge end before doing anything. With a bit of luck there won't be a solder connection there and you'll just be able to pull the earth wire through into the control cavity, and then replace it with a new one to go with your new pickup and controls.

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[quote name='BigRedX' timestamp='1456430794' post='2989041']
In the interests of keeping the original loom intact, I'd leave the earth wire attached and check how it is attached at the bridge end before doing anything. With a bit of luck there won't be a solder connection there and you'll just be able to pull the earth wire through into the control cavity, and then replace it with a new one to go with your new pickup and controls.
[/quote]
Thanks, good suggestion.

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[quote name='Hutton' timestamp='1455876822' post='2983132']
Many thanks for all the replies here folks. I've decided to fit a new loom as provided by our own KiOgon. The original bits can sit in the case.
[/quote]what pots are fitted to that?

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[quote name='dincz' timestamp='1456047704' post='2984709']


A variation that dates back to steam radio days. You can coax extra life out of an old pot by using the tip of a pencil to clean the track. The graphite is hard enough to dislodge any crusty stuff and slippery enough so as not to gouge the surface of the track. It also leaves a fine coating of graphite as dry lubrication. If you're patient and careful, it beats spraying.
[/quote]
I wouldn't really recommend this as the pencil graphite is conductive too. This could lead to an unpredictable resistance profile on the pot rotation.

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Your are correct about the pencil trick but it might be better than no law at all
On the pot.

What often happens is that the carbon ( I hate carbon pots) is worn away by the metal wiper. It is sometime possible to bend the wiper to touch an unused part of the pot's track. The worn part will reduce the value of the pot to some extent but as most pots ( and caps) found in guitars at +/-20% tolerance you won't notice the difference.

For it were me I would put OMEG or Bourns pots in, either conductive plastic or cermet. As for CTS expensive and IMHO not as high quality as Bourns and OMEG.

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[quote name='MoonBassAlpha' timestamp='1456920712' post='2993501']
I wouldn't really recommend this as the pencil graphite is conductive too. This could lead to an unpredictable resistance profile on the pot rotation.[/quote]

I wondered about this too but in practice it doesn't seem to make any difference. The minute amount of graphite dust left on the surface of the track is not enough to appreciably (or measurably) change the pot's resistance. It does work.

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