Rickresource Rickenbacker Forum

Hi all

I did a bit of a search (albeit a rushed one) trying to find someone with a similar problem but most people appear to have 'normal' hum noise.

I have a gig tomorrow night and have borrowed a mates amp (Ampeg... nice) since I only have a practice one (usually end up through a PA). When I plugged in to it last night a noticed a whole heap of noise. This is noise I hear in a PA, but it is not really a problem there as it is not very loud. The extra oomph of a real amp is obviously making my hum noise worse (around speaking volume).

The problem: bad hum noise
The weired bit... : When the volume is on max on the neck pickup, I get no noise from that pick-up, but I do get it when set to zero with the pick-up (or both) still selected. Varying the tone pot inversely increase/decreases the intensity. The bridge pick-up give a similar problem.

It is a '79 4001 but has the new wiring harness and new pick-ups (went in 2 years ago, almost to the day, by an experienced luthier/tech). Pulling out the bridge tone pot adds a bit more noise!

Anyone had a similar problem or knows a good solution?

Cheers

Matt

Sounds like a grounding problem to me. Was the harness a factory harness or made by the luthier? I would start with a schematic and the controls showing and make sure it and the grounds are right. A good closeup picture of the controls posted here would give us something to look at for a chance to see what is wrong.

And welcome aboard, Matt.

Grounding problems can indeed be a significant cause for hum and often really hard to figure out. I had a HUGE hum problem when I switched from my old Peavy 2 channel amp to my current rack setup with 2 Samsamps. The weirdest thing was that touching the outside of the Y cable connector, which is metal but NOT connected to the cable shield, would cause MASSIVE hum. When not touching the cable, I got fairly bad hum, similar to your description, where if the volume was down it was worse.

I knew I had grounding issues from the start though since my music room is in an old part of the house, built before they had grounded circuits in houses (some day I'll rewire it). But it had me a bit fooled because I did not get any hum with the Peavey. Anyway, I tried changing power cords, adding ground straps, and a few other things to no effect. Finally, I went out to the shop and dug out an old isolation transformer and plugged the whole amp setup into that instead of directly into the wall socket. Instant success, no hum at all.

So, it might be worth getting one of those little circuit checker things that you plug into the wall outlet just to make sure the wiring is all correct. It could also be a grounding problem with the amp you borrowed. If it's got a bad power cord with the ground wire broken, this could be the cause. Get an ohm meter and check to see that the amp case is connected to the ground pin on the plug by measuring from the ground pin to some metal part of the case.

I'll have a look at the grounding in the amp, although it isn't that old and the power lead looks in good nick.

Other grounding problems I have had in the past have been more obvious as you can touch the strings to ground it and it'll go quiet. It doesn't do it in this case though.