Kiloton Hum

[travatron4000]

New G&L owner. I just got a USA Kiloton. I decided to put in a Push/pull tone to add a 2nd .047uF cap in parallel as an option to tone down the beastly MFD a bit when needed. I have a similar item on my P bass.

I mocked it up and all was well, then when I went to go button it back up and noticed a hum. The hum goes away when I touch the bridge/strings/any ground point. It get's louder if I touch the front coil poles, especially in in series mode. Otherwise controls and output work as expected.

I didn't touch any of the wiring for the VOL pot or Selector witch, Just the lead to the tone knob and all the grounds that normally go there (See illustration) All the grounds are solid and tested with multi meter. I even disconnected the tone knob to test.

Thanks,

Travis

[Ken Baker]

I mocked it up and all was well, then when I went to go button it back up and noticed a hum. The hum goes away when I touch the bridge/strings/any ground point. It get's louder if I touch the front coil poles, especially in in series mode. Otherwise controls and output work as expected.

Well, there's an open ground in there someplace. Might even be a partially open connection to ground. Look for weak/bad solder joints.

--OR--

Return to standard and verify proper operation. Then replace the .047µF tone cap with a .1µF 50v polyester cap. This should give you the treble cut your push-pull gives you along with being fully sweepable from no cut to full cut. You lose the push-pull and gain a full sweep.

Ken...

[travatron4000]

Yeah, Maybe i'll just reflow all the connections. It persists with the Tone circuit removed So I don't think it's the mod. Also the mod is full tone sweep but switchable between .094uF and .047uf.

So I'm pretty sure is in the pickup wires/switch. maybe vol.

I also noticed a weird low buzz in the signal but only when playing the D string. It's there even if the note is muted. Tried different amps. Almost like a noise gate or compressor that's not working. But again only on the D string and across different amps with a direct connection.

[travatron4000]

Quadruple checked all the grounds. Reflowed everything. Same..

Anyone else get that hum when touching the coil that is wired for single use, when in Series?

[deltafred]

Could be the bridge ground connection that has gone high resistance or open circuit.

I can never remember what you are supposed to touch to make hum better or worse for a failing bridge ground connection and have found that it varies with the electrical environment you are in anyway so the only advice I offer is "check it with a meter".

To check it set your multimeter on the lowest ohms range. Short the probes together and make a note of the reading. Check the resistance between the jack body and the bridge and subtract the reading with the probes shorted. If the result is more than a couple of ohms the ground connection needs remaking.

On my Kiloton (Tribute) the bridge to jack resistance is almost zero. The metal parts of the selector switch (toggle and nut) to the jack reads about 1.5 ohms. I suspect that the switch body is grounded through the foil on the back of the pick guard hence the higher resistance, I have never had the pick guard off so could be wrong of course.

[Ken Baker]

Quadruple checked all the grounds. Reflowed everything. Same..

Anyone else get that hum when touching the coil that is wired for single use, when in Series?

<thinking>

You said hum, which if a ground is open will sound like a 60Hz hum - about a B on the A string. However, I'm wondering if you're hearing hum or single coil noise. Hum is fairly clean sounding, but SC noise can be anything that the coil can pick up from the environment, kind of like a guitar with SC pickups. If this is actually SC noise, backing off the volume and shielding may be your solutions.

You might try a tap test when in SC mode.

Set your amp's volume bedroom-style low.

Set your bass to sing coil mode. Tone about 75%, volume about 50%

Using a small screwdriver, tap a pole piece on the active coil. You should hear a clear and sharp metallic sound. If you hear a sort of distant sound that is not clear or sharp, then that coil is open at some point (not working) or otherwise not connected. Further investigation is needed. The inactive coil should sound like a dead coil.

An open coil is caused by a broken connection somewhere in its circuit. It could be the coil itself or one of the coil's leads. It could be a problem at the series/parallel switch. You get to dig in to find the fault.

More info that may help in your search:







Click the images for a PDF version.

Each of these shows the signal path, in yellow, for each of the coil select switch positions. I would trace these out visually before trying with a multimeter because of all the cross connections in-circuit.

Ken...

[travatron4000]

All the ground paths are 0 ohms clear continuity. Bridge, pots, jack, shielding, every ground solder point, bottom of the pickup (blue wire). The hum is like I'm touching the output when I touch the front coil poles. I get a bit if I pinch the yellow wire.

It's a 2020 I just got off reverb. The pup shouldn't be microphonic or anything...

Here's the weird buzz I get only on the D string
https://photos.app.goo.gl/m7JmRWwnvDmVkK638

You hear that buzz that sort of phases out after i pluck a muted note.

[Ken Baker]

If it were an active bass I'd say to check your battery, as that kind of has the sound of a battery getting pretty weak. It's also similar to the sound of a poor connection.

L Series basses that have a deep panel jack rather than a regular jack on a jack plate can have issues with the contacts inside the jack becoming worn and loose. The bass' output becomes crackly, distorted, and just overall crappy. Replace the jack and all is well again. You don't have an L Series bass and your jack is probably on a plate which should make for a reliable jack. Still, they can get grungy or have weak solder joints.

Pretty much my last gasp here because your bass isn't in front of me, but try cleaning the jack and your cable's plugs with contact cleaner.

Ken...

[travatron4000]

Pretty much my last gasp here because your bass isn't in front of me, but try cleaning the jack and your cable's plugs with contact cleaner.

Ken...

0 ohm on meter from cable ground to bridge, testing with cable plugged in.

Here's a demo video that might clear it up

https://photos.app.goo.gl/eQfmuex55My8mJuo8

[Ken Baker]

If there is clean hum in there I was unable to hear it. Probably your phone's mic not being able to handle 60Hz.

When you touched the pole piece I could hear a lot of frequency spectrum; kind of like old school fluorescent lighting.

If you still have your add-on cap in there, lift one leg and see it the bass is noisy.

In both series and parallel modes the coils are both active and are humbucking. Extreme noise can sometimes still break through. For an example, read this post.

Ken...