Volume pot bad ground

[Rich Arnold]

Hey gang,
Looks like I'm going to have to open up my Fender String master. There is an open associated with the volume pot.
I figured I may as well replace it since it's scratchy anyway and the tone pot as well whilst I got it tore down.
Can I get a recommendation as to exactly what to use as a replacements?
Thanks in advance. Rich.

[Stephen Cowell]

Rich, the SM uses a funky ground system that depends on wires stapled to the wood. The chrome panel then is screwed down onto the staple, making the connection.

I've tried bypassing this and soldering ground wires but it hums more... pretty crazy how that works.

What I've done is to lift the staple a little and wad some more wire under it, then screw the plate back down.

Here's a diagram that gives the values for the pots. Looks like the volume and mixer are 250k Audio and the tone is 1Meg linear. Fender still sells these parts I believe... check your knobs and see that you get solid, not splined, shafts.



https://www.fender.com/en-US/parts/cont ... 31000.html

https://www.fender.com/en-US/parts/cont ... 04049.html

[Jim Kennedy]

I have repaired bad grounds on a couple of early 70's Fender bass guitars. The ground for the strings was nothing more than the ground wire stripped back and laid under the bridge plate. Over time the wire is pressed into the wood, oxidation forms, no more ground.

You must make a solid connection between the wire and the chrome panel. If you have more than one ground under your panel, make sure they are solidly connected. To connect to the chrome panel, I use a small ring connector, and then run one of the screws for the plate through the connector, and screw down tightly.I have also seen other makes of guitar where the ground was soldered to a bridge plate or face plate to make solid connection.

If this does not help, check all of your ground connections with an ohm meter. Any reading from your chrome plate to any ground connection should read nearly zero on the lowest range. Any reading from point to point along your ground should be the same. We are dealing with thousandths of a volt audio signals. It doesn't take much resistance to kill your signal.

[Ron Pruter]

Always be aware of the "Sweet Spots" when playing. This may not be your situation but on many stages, just turning and facing slightly to the left or right makes the hum just about disappear. I really find this helpful when recording.
The test for open ground is-When you grab your strings, the hum doesn't get quieter. If it doesn't, there is an open ground. RP