Low Signal, High Hum

theAeronought

New member
Alright, I soon as I start talking, you're going to start thinking, well of course you've got a low signal and a lot of hum - those pickups are ancient! But let me tell you, this is no ordinary hum, and I know these pickups can be louder.

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I borrowed the body and neck of my brother's Epiphone Les Paul so that I could try out these old Teisco pickups I found on craigslist. I took out the pickups and the wiring and the pickups, wired up my own harness (incidentally from a lefty LP that I scrapped for parts last year), and made adapters for the pickups so they'd fit over the humbucker routes. I also had to solder new wires to the old leads coming off of the pickups because they were too short to reach the other components. Then I plugged it in - at first, nothing at all. No hum, no noise, no beautiful miraculous clean jangliness, nothing.

So the next day, I took the access panel off again and tried a few more things - resoldered connections some connections, compared what I had done to several wiring diagrams, including the one I took out of the LP to begin with (which was identical, only with single-coils in place of humbuckers), re-attached the wires to the pickup leads, everything I could think of. There were a couple weak connections to begin with, so I thought this would do the trick. Put the access panel back on, plugged it in - still nothing. There goes my weekend

Today I tried something new - I took the access panel off and tried to play it like that, and SWEET LORD, THERE WAS SOUND. IT WAS A SOUND LIKE NO OTHER, THAT SANG TO MY SOUL, even if it was a little quiet. This was, I now think, as good as it will get. I had to turn the amp up to double what it had been (that's not much, it's just a little 10-watter) to hear it as loud as my other guitars, but that's alright. The problem is, that sound is now GONE. Of course I had to fix whatever problem there was - everytime I put the access panel back on, the signal sputtered and died, and I can't go around with wires hanging out the rear of my guitar. I spotted what I figured was the problem - one connection was still a little loose, and whenever I squashed the wires into the control cavity, the connection would break. So I fixed that up, and now the signal is very weak, and the hum, not so much.

What am I doing wrong?! Can anybody think of a potential diagnosis for what's up with my wiring, that isn't just old cheap pickups?
 
Re: Low Signal, High Hum

Measure the DCR of the from the metal parts (bridge, pup covers) to ground. maybe you have a bad gound. is there a ground wire from the bridge to the pots?
 
Re: Low Signal, High Hum

Measure the DCR of the from the metal parts (bridge, pup covers) to ground. maybe you have a bad gound. is there a ground wire from the bridge to the pots?

It is vaguely possible there is a bad ground. It occurred to me yesterday that there is a wire coming from the pickups that is strictly for grounding - what I did with that was to stick it in the same hole with the mounting screw and grind it into the wood. I knew it was unreliable, so I'm going to scrap the paint off a patch of wood in the pickup cavity and solder the wire there. Think that'll do it?

Also, excuse my ignorance, but I haven't needed to check DCR on anything yet - do you just stick the two ends of a multimeter on the metal parts?
 
Re: Low Signal, High Hum

Put one meter probe on the pickup's hot lead and the other on the ground lead. Obviously dial up Ohms (rather than voltage or current, etc). And, of course, turn the meter on...
 
Re: Low Signal, High Hum

Put one meter probe on the pickup's hot lead and the other on the ground lead. Obviously dial up Ohms (rather than voltage or current, etc). And, of course, turn the meter on...

To tack on to this comment. A set of alligator clip leads really helps when doing this kind of testing. Clamp one end to the meter and the other to the pickup. Much easier than trying to hold the wire.
 
Re: Low Signal, High Hum

It is vaguely possible there is a bad ground. It occurred to me yesterday that there is a wire coming from the pickups that is strictly for grounding - what I did with that was to stick it in the same hole with the mounting screw and grind it into the wood. I knew it was unreliable, so I'm going to scrap the paint off a patch of wood in the pickup cavity and solder the wire there. Think that'll do it?

Im not sure I understand you, but if I do, nope. You don't ground to wood. You connect all grounds to form a path to the sleeve of your output jack. Wood is not usable for a ground.
 
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