G&L Wiring Help

[Mammoth_Bass]

hi everyone,

I just purchased my second ASAT bass; a Tom Hamilton! I love ASAT basses and couldn’t say no when this one presented itself. However, I am having a small issue. When I am in series mode there is a significant amount of 60 cycle hum. Process of elimination shows that the bridge pup seems to be the culprit. I do not see any loose or broken solder joints in the cavity and ensured that the bridge ground is secure.

My other ASAT is dead quiet in series mode so I know this isn’t typical hum. I am hoping someone out there has an idea for me!

I have a poorly done YouTube video to demonstrate the issue. Please don’t mind my dogs crazy noises in the background or my hair wrapped in a towel

 

[Killed_by_Death]

Sounds like my bass used to in the single-coil switch position.
I'm not sure how it could have happened, but it sounds your switch is putting it in single not series, but it could be some contacts shorting out.

Here is G&L's own wiring diagrams page:

G&L Wiring Diagrams and Schematics

From there you can get this drawing & compare the wiring in your bass:

 

[Axstar]

Oooh new wiring thread! Ah, @Killed_by_Death got there first. Never mind.

 

[Killed_by_Death]

It gives me pain to know G&L could have dispensed with the treble boost position by just using 500K Ohm pots for volume & treble cut.

 

[Mammoth_Bass]

Sounds like my bass used to in the single-coil switch position.
I'm not sure how it could have happened, but it sounds your switch is putting it in single not series, but it could be some contacts shorting out.

Here is G&L's own wiring diagrams page:

G&L Wiring Diagrams and Schematics

From there you can get this drawing & compare the wiring in your bass:

View attachment 3146743

Is it ok to pull off the pre amp which appears to be held by some adhesive? That way I can get a better look at the cavity

 

[Killed_by_Death]

I recently was looking at my own L-2000 & the preamp is stuck on there pretty good.
TBH I don't think your trouble spot is under there. It's with one of the switches most likely.

If you do decide to pull it up, I'd get a butter knife or something similar, slip it in between the adhesive & the pot back & twist it a little, prying it up slightly.
Do that all around it & eventually it will come off a little easier.
If you just pull up on it until it comes loose, you risk yanking the wires & creating a new problem.

This is what mine looks like:

 

[DavePlaysBass]

Is the bass from the era with the big green "chiclet" capacitors. The original Leo design puts the big green caps at the junction point of the series connection to ground. It sucks the highs out of one of the coils and gives you the lows of two coils. The G&L heads call it the OMG (oh my God) mode or single coil with bass boost. G&L stopped using the caps on stock basses around 2005ish. But G&L aficionados love to mod the hell of them so no telling what you have.

These caps caused series mode to hum. It would be weird but it may be that the OMG cap is there on the bridge coil but someone removed it on the neck coil? Look at the series / parallel switch with 12 lugs. Are there any caps going to it.

I probably cannot post to another forum from here, but if you are going down the road of series coil possibilities and G&L, I have posted a how to document at the forum to not be named. Series mode can be made hum cancelling with the caps if modified the right way. Drop me an IM if interested...