Volume pot won't stay at 0. Fixable or replaceable?

Tall_martin

Hi,

I took a strat type guitar I bought in lockdown to practice last night. 

Its volume pot wouldn't go to 0. I've had it a year or so, but as it only gets used at home the volume has just stayed on full. It went from full to 1/3 volume but where it should be silent it was about 1/3 volume.

I'd prefer to fix it in one go as I'm a bit time poor at the moment. Is it likely to need a whole new volume pot or just some soldering touching up?

It appreciate this might be a how long is a piece of string question! My soldering is "functional" at best so it would be good to have an idea if it is likely to be possible to fix it before replacing it.

The guitar is a vintage Joe doe strat type I bought new if that makes a difference.

Thanks for any help

PrecisionGuided

Could be the pot, could be the wiring. 
It's worth having the scratch plate off to check the wiring - a poorly soldered earth could be the culprit. Use a croc lead to jumper the vol pot's ground lug to the jack earth - any better?
You'll have to unsolder the vol pot to test it with a meter. Measure resistance between the outer lugs (250K ish?) and then between the centre lug and an end lug as you rotate the pot - it should be 0K to 250Kish.
If it's a faulty pot it's a cheap and easy replacement...

Tall_martin

Thanks!

BillDL

I'm not sure I understand what you are describing.  If I have picked you up correctly, you are saying that when the volume pot is rotated fully anti-clockwise where it would usually cut all sound, you are left with what you estimate to still be about a third of the volume level.

Do you remember from any other times when you last played it whether the volume pot was a very gradual taper until it was just a whisper before it hit zero, or is there a chance it was still allowing some sound through (even up to a 3rd of the volume) just before the last little bit of rotation before cutting the signal?

If that was the case, then it could just be some grit or grime or oxidation preventing the contacts from making full contact at the zero position and not silencing the signal.  That kind of issue can usually be solved by rotating the knob fully in either direction for quite a while, and usually a small squirt of solvent electrical contact cleaner through into the potentiometer's body (the can) in combination with repeated rotation will help to dislodge crud.  Suggested contact cleaner:

Servisol Super 10 switch cleaning lubricant.  That's the most readily available of similar sprays by other companies.

Tall_martin

I'm not sure I understand what you are describing. If I have picked you up correctly, you are saying that when the volume pot is rotated fully anti-clockwise where it would usually cut all sound, you are left with what you estimate to still be about a third of the volume level.

Yes. Exactly

Do you remember from any other times when you last played it whether the volume pot was a very gradual taper until it was just a whisper before it hit zero, or is there a chance it was still allowing some sound through (even up to a 3rd of the volume) just before the last little bit of rotation before cutting the signal?

I've just played it at home on full volume. So not sure

switch cleaning lubricant

I've got some of that kicking about, I'll give that a go first 

Funkfingers

If an audio taper pot reduces volume until the wiper contact passes halfway, then, jumps back to full volume, there is probably damage to the resistance track inside the pot.

"Damage" could mean the dirt and/or corrosion suggested by BillDL or it could be the contacts failing to, er, contact.

Fixing the pot internals properly involves opening up its casing. 

If the semi-functional pot is some dogbreath Korean or Chinese budget item, you might as well just replace it and enjoy improved functionality.

ICBM

That's the result of the ground connection being poor. Usually this is caused by the contact between the ground terminal and the trackboard not being very good - often strained when the terminal is bent back to solder it to the casing. You can usually fix it by squeezing the rivet hard onto the board with fine-nose pliers.

If that doesn't fix it, the trackboard is cracked and you will need to replace the pot.

Tall_martin

Thanks all for the ideas.

So far I've had time to try the contract cleaner. This almost worked for 10 seconds and then it went back to not reducing the volume.

So I'm going to have to open it up and unsolder the volume pot to test it/bend it/ resolder it I might as well get a  new volume pot while I'm at it. Does this look ok for a £5

Borne pot

https://www.axetec.co.uk/guitar_parts_uk_052.htm

Funkfingers

Bourns pots are well respected. Regular Stratocasters require audio taper 250k pots for all three controls. If you want to add fancy switching options, order a push-pull or push-push type.

Dave_Mc

Tall_martin said:

Thanks all for the ideas.

So far I've had time to try the contract cleaner. This almost worked for 10 seconds and then it went back to not reducing the volume.

So I'm going to have to open it up and unsolder the volume pot to test it/bend it/ resolder it I might as well get a  new volume pot while I'm at it. Does this look ok for a £5

Borne pot

https://www.axetec.co.uk/guitar_parts_uk_052.htm

What pots does your guitar currently have? I would guess if it's a vintage they'll be metric-sized (but check to be sure). It's an easier swap if you go for something metric sized (I think the Bourns is imperial). You can get CTS Metric-sized pots at Axes-R-Us, for example. EDIT: Or you could just do the sandpaper thing which Axetec suggested with the Bourns one... 

ICBM

Tall_martin said:

So far I've had time to try the contract cleaner. This almost worked for 10 seconds and then it went back to not reducing the volume.

That does sound like a contact problem not a broken trackboard.

Tall_martin said:

So I'm going to have to open it up and unsolder the volume pot to test it/bend it/ resolder it I might as well get a  new volume pot while I'm at it.

You don't need to unsolder it or even remove it from the pickguard to try the pliers trick.

This is a very common fault, it puzzles me why it (and the usual solution) aren't better known...

Tall_martin

You don't need to unsolder it or even remove it from the pickguard

Ah. I've bought the new pot and it's on route.

If the bending doesn't work I'll have the new pot to swap in anyway. 

I can't imagine I'll never need to swap a volume pot and it's not like it will go off sat in a drawer.

ICBM

If you do fit the new pot, don't do what causes this problem and just bend the ground terminal back with you fingers to solder it to the casing - instead, use pliers to bend it halfway up so it forms a near right angle, which avoids straining the rivetted connection to the board.

Tall_martin

Thanks @ICBM !

I took it to bits and have the pot a squeeze with pliers and it works perfectly now

Tall_martin