Strange problem with volume control

[brokenstick]

Hi, my first post here, although I will be posting some pics of my build soon

I have just about completed building a TL kit and have a strange problem with the electronics. Everything works, however have 2 things happening that seem strange to me.

1. When volume is on full or off completely the guitar is silent, ie no background hum, which is good. When volume is in the middle though there is a significant hum. So when turning the volume knob from 0, hum increases as volume increases, until it reaches the middle when it then start decreasing and is gone when it reached full

2. There is no hum when selector switch is in the middle, however slight hum when in either bridge or neck pickup position
This hum is a much lower hum than in 1. above.

So overall best situation is with volume on full and switch in the middle, guitar is then almost completely silent

Any idea what might cause this?

I shielded all the cavities and be the pick guard with aluminium tape, and connected them and tested all over for continuity with a multimeter, so think my shielding is pretty good

Thanks

[Simon Barden]

Hi and welcome.

I take it that the volume control actually works and that you do get a reduction in level as you turn it down?

Assuming that, it sounds more like either a high resistance solder joint or a bad guitar cable. Hopefully you aren't using the guitar lead that came with the kit, as they are awful and should be thrown straight in the bin. The outer braid on them is a few whispers of wire with big gaps in between them and provides very little shielding for the signal wire in the middle.

Passive guitar pickups make a high impedance circuit and high impedance circuits are prone to picking up far more noise than low impedance circuits. So anything that increases the circuit impedance, such as a poor solder joint, increases the system impedance and makes it more prone to picking up noise.

With the volume knob at 10, you've got maximum output signal, so the best signal/noise ratio. With the volume set to 0, the output signal is grounded so any noise is also grounded, hence no noise. But with some dodgy connection and a lower signal output, you will be prone to more noise.

It's highly probably that one of the pickups is 'reverse wound/reverse polarity' (RWRP) with respect to the other (the magnet's polarity is flipped and the signal is sent the other way around the coil). This isn't always the case with pairs of single coil pickups, but it would explain the lower noise level with both pickups. With one pickup being RWRP, its signal output ends up being the same polarity as the other pickup, but any noise picked up is reverse polarity with respect to the other pickup, so the two noise signals cancel each other out to a large extent. You effectively create a humbucker pickup with widely spaced coils (but with the coils wired in parallel as opposed to the standard series coil connection of a humbucker so the sound is thinner).

So you need to track down what is probably a poor ground connection. Have you got a multimeter? If so, check the ground connections from the output jack back to all the ground connections on the TL wiring e.g. backs of pots and the control plate. resistance should basically be as low as your meter measures with the probes shorted.

If not, you could start out by simply redoing all the solder connections.

Posting some pictures of the wiring and shielding will help us to see if anything obvious is amiss. I know its partly pre-wired at the factory, but they don't always get it right.

[brokenstick]

Thanks, really appreciate the detailed response.

I haven't even opened the cable that came with it, but will take your advise and chuck it out! The cable and amp work fine with other guitars so don't think there is any problem there.

I have a multimeter and did test the grounding but am now doubting myself and will check it again.
I think my soldering on the back of the volume pot leaves a lot to be desired so that could well be the issue.
Some pics below. I actually ripped offl all the shielding shown in the pics and did it again much better, so disregard that. i also ran some bare copper wire between the cavities and tested continuity

[brokenstick]

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[king casey]

Hopefully you aren't using the guitar lead that came with the kit, as they are awful and should be thrown straight in the bin.

Whoah!! So hasty and wasteful. The one I've got is working perfectly.

cheers, Mark.

[JimC]

Or make it your 'lend to strangers' lead.

[king casey]

Or make it your 'lend to strangers' lead.

The thing about this global pandemic is that my life hasn't changed much.

cheers, Mark.

[Simon Barden]

All the connections look OK and the output jack is correctly wired.

What solder did you use? The pre-wired stuff will be using lead-free solder. I still use 60/40 lead solder at home as it's easier to use and melts at a lower temperature, so is less damaging to electronic components. But it doesn't mix with lead-free solder, so if you are using leaded solder, then I'd make the back-of-pot connections on a different part of the pot to be sure of a good electrical connection.

But if your ground path resistance measurements are OK, then it may be down to a damaged volume pot (though I've not experienced this particular issue before). I'd be tempted to get another couple of mini pots (250k log/audio short split shaft - 18 spline) and re-do the controls. I'd also modify the pickup leads so that there was a short length of braided wire that goes to the rear of the volume pot and a much longer length of the insulated central core signal wire that runs to the selector switch. It saves having to use masking tape to stop any inadvertent signal shorting.

[Simon Barden]

Whoah!! So hasty and wasteful. The one I've got is working perfectly.

cheers, Mark.

It may work, but it really is a very poor cable.

Here's a kit guitar lead cut open. It really is only barely doing its job. You've got a thin stranded ground wire that's very loosely wrapped around the central core, but with huge gaps in its coverage and protection. It's slightly better than using twin core power lead, but not by much. When the cable bends, those gaps open up even more:


Here's a slightly better quality guitar lead, the basic sort you get from a music shop. It's got about double the amount of shield wires wrapped around the core, but it's still only a single layer wrap, and it too will have the screen open up more on bends, letting in more noise. But it's still a lot better quality than the kit lead:


And here's a Planet Waves lead I sacrificed to take a photo of a good quality lead. This is the sort of double helix, tight-wound, braid screen you would expect on a good quality lead. No gaps in the shielding and the construction means that you won't get gaps opening up in the braid when it bends:


And all three together for comparison:


There really is no point in trying to screen the control cavities on the guitar, making sure there are no gaps, if you insist on using poor quality guitar leads. A good quality lead with Neutrik or Switchcraft jacks and say Van Damme cable, can be had for less than £20 in the UK via Amazon, and costs even less if you make it up yourself. This was the last lead I bought, and includes a silent connector on one end. https://www.amazon.co.uk/gp/product/...e?ie=UTF8&th=1

Don't make your guitar cable the weakest link in your signal chain.

[fender3x]

I was thinking about using mine as a shielded wire that could use to connect pots in an ES style guitar. When I saw what Simon has in his pic, I tossed mine. Rare to find something that is too much of a POS for even me to find a use for.