Strange Problem with Thunderbird Bass Buzzing and Low Output

[PoorMan]

I'm working on my buddy's Thunderbird bass that has some odd electrical gremlins I haven't been able to track down thus far. Any suggestions would be greatly appreciated.

Problems:
1. Low/weak output.
2. Buzzes loudlly when tone pot is at 10 and eventually disappears when turned down.

Confirguration is 2 'buckers, voulme, volume, tone, output jack (no switch).

In circuit, both pickups measure somwhere in the 4k range. They should be 9k+ (not absolute numbers...I'm operating off memory). But the point is they measure almost exactly half the expected output. When removed from the circuit...they measure properly. I know the circuit itself lowers the resistance reading...but I've never seen it drop by half.

For buzzing: I checked the ground through the entire circuit and it's fine. It's only the tone pot so I replaced it but the problem still exists.

I'll also say this...I am used to the Fender/Gibson standard switchcraft style jack with 2 poles...this one has 3 and one pole is not wired up. I think it's just a stereo jack, but I have no experience with them and can't find any circuit info on modern Thunderbird basses.

Thoughts?

 

[BloodRose]

Re: Strange Problem with Thunderbird Bass Buzzing and Low Output

Wish I could offer help. I have a Tbird pro that has active pups. So, Ill give you a bump..

Bassmedic? Any thoughts??

 

[PoorMan]

Re: Strange Problem with Thunderbird Bass Buzzing and Low Output

I realized the output issue is because the pickups are wired in series in the circuit...so when both volumes are at at ten the output drops significantly. So that's a non-issue.

I replaced the pots, cap and rewired the entire circuit. Still buzzes like crazy.

The pickups are potted in epoxy so I can't confirm this, but I'm wondering if they aren't humbuckers?

 

[Wonker]

Re: Strange Problem with Thunderbird Bass Buzzing and Low Output

Where is the body ground?

This is going to sound dumb but make sure the ground wire is on the right prong on the input jack.

 

[PoorMan]

Re: Strange Problem with Thunderbird Bass Buzzing and Low Output

Where is the body ground?

This is going to sound dumb but make sure the ground wire is on the right prong on the input jack.

The ground originates at a bridge stud (like a Les Paul). I checked the ground direct to the bridge and it's ok.

The jack thing doesn't sound dumb at all. I thought it might be the jack because it's a jack style I have not worked with before, but I installed a standard switchcraft jack and it still buzzed...so that's been ruled out as well.

I think I've ruled out everything except the pickups. I may install one of my humbuckers and see if it quiets down.

 

[Wonker]

Re: Strange Problem with Thunderbird Bass Buzzing and Low Output

Take a few minutes and wire each pickup individualy straight to the jack.

 

[PoorMan]

Re: Strange Problem with Thunderbird Bass Buzzing and Low Output

Take a few minutes and wire each pickup individualy straight to the jack.

Excellent idea...that will rule out any other gremlins. :beerchug:

 

[Wattage]

Re: Strange Problem with Thunderbird Bass Buzzing and Low Output

Check the jack, they are very screwy and cause weird issues when they break