#1
Hi. I just wired up a friend of mine's guitar, and all seems to be well, except for the extraordinary amount of hum/crackling! It is a dual humbucker guitar. I have already triple-checked all ground connections. The guitar works in all switch positions, but when the tone pots are completely turned up, there is a lot of hum/crackling. If I turn the tone knobs down completely (either one, depending on switch position) it completely kills the hum and I have a clean sounding guitar. Any ideas why this may be happening? Could this be bad caps? I did re-use old ones for this guitar, using a heat-sinking alligator clip when making connections.

Thanks!
#2
definitely could be bad caps
just get new ones, they are pretty cheap
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Last edited by justinb904 at Oct 2, 2009,
#3
Quote by Mirakus
Hi. I just wired up a friend of mine's guitar, and all seems to be well, except for the extraordinary amount of hum/crackling! It is a dual humbucker guitar. I have already triple-checked all ground connections. The guitar works in all switch positions, but when the tone pots are completely turned up, there is a lot of hum/crackling. If I turn the tone knobs down completely (either one, depending on switch position) it completely kills the hum and I have a clean sounding guitar. Any ideas why this may be happening? Could this be bad caps? I did re-use old ones for this guitar, using a heat-sinking alligator clip when making connections.

Thanks!



Its probably high frequency hum. The tone pot and cap are there to filter out high frequencies, so when you turn the knob thats why the hum is going away. I'd say its a ground problem or a bad soldier connection.
#4
Tone pots always reduce hum when you turn them down.

The hum is mostly high frequencies. Tones shunt high frequencies to ground. Therefore, hum is reduced when the tones are turned down.
#5
Doh...dummy mistake! I had the polarity of the connections on the input jack reversed. That solved that problem, but somehow it still worked, so it may be of help to someone else who someone who is having a similar problem.

Now I have a new problem! When the switch is in the bridge position, turning the volume knob down all the way does not kill the sound! In the middle pos, killing the neck volume turns of the sound, but if the bridge vol is all the way up, the sound peaks in the middle of the pot! If I turn the bridge pot down, the neck pot functions normally.

This seems to me like it could be reusing old pots causing the problem, but I was also thinking it could be the switch, which is the standard 3 position variety. Also, I checked the resistance of the pots before wiring and they were all ok.

Has anyone else encountered this before?
Last edited by Mirakus at Oct 2, 2009,
#6
Did you check the taper?

to do this just put the ohm meter on the first and second lugs (looking at the shaft side) and rotate the pot very slowly while watching your meter. analog meters are great for this.

if the meter doesn't act funny or sporadically jump up or down, the taper is good.

all I can really say atm is check the solder joints. did you ground lug 1 (looking at the shaft side) of the volume pot?
#7
I did check the taper, but I noticed the should-be-grounded lug had a crappy connection. I'm going to try soldering that into place and I'll let everyone know how it works out. I think that's it! Thanks! I've been trying to get it done so fast I've been overlooking stuff.
#9
Grounding the other lug did fix the volume problem. There is still the issue (while mysteriously only in the middle switch position) of the neck volume peaking in the middle of the pot, but I'm just going to conclude it's a crappy pot at this point, or possibly switch. My buddy didn't actually buy any new components, so I was forced to work with all used stuff.

Thanks for all the help!
#11
I'm not sure exactly...it has the 3 positions similar to the LP style, but I can't actually see the contacts because it's all in a rectangular enclosure. The guitar was an old Electra-Westone my friend found in the trash, so I'm not sure of my chances on finding the exact same switch to replace it.