Bad Hum from pickup

Mick Ostrander · From: Illinois, USA

Initial Disclaimer: I am a total noob to the world of pedal steel. With that said, thanks in advance for your assistance.

I recently acquired a Carter Starter guitar. Upon plugging it in to the amp, I immediately noticed a bad hum, much more than would be expected from a single coil pickup. I have tried different amps and other guitar cords and have found the same result.... bad hum.

I would greatly appreciate any insights to this problem and suggestions for correcting it. I am guessing a bad ground, but how do I go about fixing it? Everything looks normal on the underside of the guitar. Thx.

Stephen Cowell · From: Round Rock, Texas, USA

Mick, your first step involves an ohm-meter... if you don't have one, you should get one... it only costs about $15, and will save lots of money at the tech's. Get one with Auto-Range if you can afford it... it will save lots of headache while you're learning to use it.

You need to ohm your pickup... to do this, set your meter to 'Ohms' and verify you're getting a good measurement by testing the meter with the probes open, then shorted together... you should see a big difference! The meter will read something like OL (over-load) when open and something like 0.2 (very small) when the probes are touching each other.

Next plug a 1/4" cord into the guitar and put the probes each on tip/sleeve (doesn't matter which)... you should be reading your pickup ohms now. 15000 to 25000 would be normal for a PSG... less for a lapsteel. K means x1000, so 15K would be a normal pickup.

I'm guessing that you're reading overload, or 'infinite' ohms... this indicates an open connection, either outside (you hope!) or inside (you don't want) your pickup. You can trace back through by holding one probe on the 1/4" plug and testing the connections inside the guitar... if you find that you never get a decent ohms reading you will probably require a rewind (or replacement). Test both the tip and ground connections as far back as you can... the ground should also show very low ohms to the guitar's frame.

Ohms-meters are useful for testing lots of things... learning to use one can save lots of money and perhaps even start a new career! Good luck.
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John Broughten · From: Minnesota, USA

Stephen, I read your response with interest. You mention that a PSG would have 15000-25000 Ohms and a lap steel would be less. How much less would be normal for a single coil pickup on a lap steel? I also am trying to find the source of a buzz/hum. Thanks.

Stephen Cowell · From: Round Rock, Texas, USA

I've seen everything from <2kohms (Rick) to upwards of 10Kohms (Stringmaster)... big wide variance here. If we had your exact model and measurement we could compare with the immense resources of our combined membership... or at least we could argue about it!

Bad hum (without nearby noise) normally indicates an open circuit, either inside or outside the pickup. Grounding the strings often helps... there should be a wire going to the string claw from the jack ground. Shielding of the pickup/electronics cavity helps too.
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Mick Ostrander · From: Illinois, USA

Thanks for the advice regarding the bad hum problem I was having. As it turned out, my problem was being caused by having the amp on a house circuit that was being shared by some lights that were using a dimmer switch. When a moved the amp to a different circuit, the hum was nearly eliminated. I greatly appreciated Stephen's suggestion regarding the ohm test. I was advised to keep the amp away from florescent lights and computers as well. Learned something new. My pickup tested out at 17,000 ohm. As the saying goes... try the simple stuff first.

David Shepack · From: New Jersey, USA

My Maverick produces a usable sound but has a hum unless I remove the 1/4' jack from the maverick chassis and just let it hang there. Any ideas on what could be the problem, or have any other Maverick players come across this issue?

Stephen Cowell · From: Round Rock, Texas, USA

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Yep (What Stephen said) Wink

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