Quick question - checking pots with multi meter

terada

Hi everyone,

I’ve been trying to check the resistance of the pots in my R9, and while I’m getting a reading for the two tone controls (532 bridge and 508 neck),  not sure how to test the volume controls. 

Anyone know what I should expect to see for these, and which lugs I should be testing? The outer ones keep reading 0 and the middle and outer appears to go up until to aroun 115 until you reach about 8 on the dial, and then drop off 

the meter is set to 2m

terada

Also wondering whether using the multi meter could potentially damage anything ?

John_A

Should be the same as the tone controls measured between the 2 outer lugs.  A meter wont hurt anything

gringopig

.

springhead

Yep, you can only measure the tone pots without any unsoldering.  

ICBM

springhead said:

Yep, you can only measure the tone pots without any unsoldering.  

No, you can measure the volume pots too, but it requires a bit more maths.

Put the selector switch in one or other pickup position, not the middle. Connect the meter to the end of a cable plugged into the guitar, from tip to shield.

Turn the volume control to 0 - the meter should read 0. Turn it to 10 - the meter should read the DC resistance of the pickup.

Now turn it slowly between the two - the resistance will rise to a peak, then go down again. Find the peak value by carefully turning it back and forth until you're sure you can't find a higher reading. Then multiply that number by four, and subtract the resistance of the pickup.

(This does assume that the pots are wired the normal Gibson way - if they're wired 'backwards' like a Rickenbacker, Jazz Bass or some far-east Gibson copies, simply turning the pot to zero will give you the pot value.)

terada

Thank you everyone for your comments. I can see now why it wasn't working for the volume pots!

@ICBM, would this also be possible using the middle and side lugs themselves, as I have noticed these will give a reading of c.115 with the pot turned to ~8?

terada

Ok following ICBMs notes I'm getting the following:

Neck Volume: 138 x 4 = 552
Bridge Volume: 134 x 4 = 536 

Both pickups appear to be 7.7 when I set the meter to 20k. So that would make them 544 and 528

Does that seem sensible?

ICBM

terada said:

@ICBM, would this also be possible using the middle and side lugs themselves, as I have noticed these will give a reading of c.115 with the pot turned to ~8?

Yes - that's the same as using the plugged-in cable when the switch is set to one pickup only. The great thing about doing it with the cable is that you don't even have to open up the guitar.

The reason it works is that you're measuring half the resistance to ground in two directions, one via the lower half of the pot track and one via the upper half of the track and the pickup. These are effectively in parallel, so the result is a quarter of the total resistance of the pot track + pickup.

terada said:

Both pickups appear to be 7.7 when I set the meter to 20k. So that would make them 544 and 528

Does that seem sensible?

Yes. That's well within the usual tolerance for a 500K pot.

terada

ICBM said:

terada said:

@ICBM, would this also be possible using the middle and side lugs themselves, as I have noticed these will give a reading of c.115 with the pot turned to ~8?

Yes - that's the same as using the plugged-in cable when the switch is set to one pickup only. The great thing about doing it with the cable is that you don't even have to open up the guitar.

The reason it works is that you're measuring half the resistance to ground in two directions, one via the lower half of the pot track and one via the upper half of the track and the pickup. These are effectively in parallel, so the result is a quarter of the total resistance of the pot track + pickup.

terada said:

Both pickups appear to be 7.7 when I set the meter to 20k. So that would make them 544 and 528

Does that seem sensible?

Yes. That's well within the usual tolerance for a 500K pot.

Perfect. Thanks so much for your help - learn something new every day on this place!

springhead

Yes, that's a cunning method, very good!