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volume pot.

A

Asa Samuel

Apr 9, 2007
3,722
3
33
Cornwall, UK.
#1
right, i know basic electronics but not guitar electronics.

i have a westfield jazz bass with two volume pots and one tone.

The top volume pot isnt working so i need to replace it. i know how to hook it all up but i dont know wich one i need to get, (250k, 500k 300k ect.) so how do i work it out or can anyone tell me?
 
#4
right, heres what happens, every so often if my bass gets knocked even slightly the volume pot reverses.

so normall i turn it clockwise, when it reverses two things happen, one i have to turn it counter-clockwise and if i turn it normally it mutes everything.

the other is it sounds like the gains be turned up loads so things like finger noises are up really high.

i do use a chorus pedal but its definatly not that thats making this change as there are no wires out of palce.
 
#5
FWIW:

Chorus pedal's a no no: the ONLY reason you'd have a chorus pedal in the chain is to test it as the source of the problem. If you don't know why then read FAQ Dimento's Trouble Shooting Guide.

Pots don't reverse themselves and I've never experienced it or heard of it happening so either it's probably either malfunctioning, is miswired, or both.

Who wired the bass and when?
 
#7
FWIW:

so the bass should be original if bought new - which doesn't necessariy mean it's wired properly. Given the assumption it was bought new then either it's been a while and something's changed or it should be covered by the seller.

Some manufacturers have wiring diagrams on their site for their respective instruments so that would be worth a check. If so you could compare it to what you've got.

The fact a bump alters function indicates a poor connection somewhere in the circuit.

The trouble shooting guide says the rest. Passive jazz is likely 250K audio pot.
 
#9
What does it have in it for pickups? If you don't know try to post Pictures. General rule of thumb Single coils get 250k and Humbuckers get 500K. This is not a hard and fast rule and the only difference will be with the 500K it will sound briter than with the 250k. It will not damage anything. I have been around electronics for many years and have never heard of pots reversing themselves. If there is anythingelse in the line between the bass and the amp remove it and see if it still does it.
 
#11
I have a possible theory:
There is a loose connection in the ground between the output jack and the pickup ground.

Look at the Seymour Duncan wiring diagram in this post:
http://www.talkbass.com/forum/showthread.php?t=336704

If wired exactly like the diagram and there is no other connectivity between the vol pot ground, i.e. the pickup ground, and the output jack then the volume control should work in reverse. This is because the output jack sees the output of the vol pot against the output of the tone pot. When the vol is up full then there should be very little potential between them (depending on the tone setting). If the volume is down, then there should be almost full pickup potential between them.

What it's missing is an definite ground connection between the vol pot and the tone pot so the output jack sees a ground connection straight through to the pickups.

Perhaps with a bad solder and a loose wire in a pot lug or something, bumping the bass can alternately make or break the ground connection.
 

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