Les Paul rewire - Reusing switch & jack from PCB?

NCo

Hi guys,

I have a LP studio I am about to rewire. It has a PCB board and started humming like mad, nothing I tried manage to fix the issue so I'm replacing the whole lot.

I was wondering whether the jack & switch are reusable? I was positive they are as I can not see a reason otherwise, but one person told me they aren't, and another said it depends on how they connect to the board.

Any help would be appreciated.

Thanks.

Headphones

They'll likely be fine, the ones on my SG seemed pretty good and the switch remains giving excellent service after quite few years.  The jack is part of the board on the SG though - and was damaged by Gibson's installation as the body's too shallow to fit the PCB/Jack and cover...

 I'd strongly reccommend determining the reason for the humming first, you may not solve the problem.

ICBM

Yes they are. The jack isn't on an SG as it's mounted to the PCB as well, but the switch is on both of them.

As Headphones said, first make sure the issue isn't with the jack or the switch wiring though. Even if it is the PCB, it's likely that it's the connectors and not the PCB itself. I fixed one with an intermittent buzz problem like this - 



- which also noticeably improved the tone, and without needing to spend money on new parts.

NCo

Now that I think about it...

The guitar was hum free until it returned from a setup. I asked they guy to check if I can remove the humbucker covers, so he may have disconnected the connectors, although unlikely.

He also 'fixed' the movement of the toggle switch and added the poker chip. This leads me to believe that the issue could either be with the switch or pickup connectors.

Question is, what further tests can I do? I checked each and every connection, including the ground wire, but the hum is still there.

Looking at the image, do you think both are reusable?

https://ibb.co/9yfj8pm

Winny_Pooh

You have a multimeter? Are you getting continuity from the strings to ground, ground to the jack output from the pots and pickups?

NCo

Winny_Pooh said:

You have a multimeter? Are you getting continuity from the strings to ground, ground to the jack output from the pots and pickups?

No, I don't. Have you got one you could recommend please?

ICBM

I would try to fix it rather than replace all the components, as the push-pull switches make it more complex than a standard wire-up. There's a very high chance that it's one or more of the connectors that's the problem, and you can bypass them as I did with that SG.

The first thing I would do is touch the braid of the jack cable directly to the back of the bridge tone pot under it. If that fixes it, solder it down permanently there.

When you say hum, is it more of a buzz?

Does touching the strings change or stop it?

Does it happen on both pickups or only one?

NCo

ICBM said:

I would try to fix it rather than replace all the components, as the push-pull switches make it more complex than a standard wire-up. The first thing I would do is touch the braid of the jack cable directly to the back of the bridge tone pout under it. If that fixes it, solder it down permanently there.

When you say hum, is it more of a buzz?

Does touching the strings change or stop it?

Does it happen on both pickups or only one?

I think it's a hum.
Touching the strings, bridge or output jack eliminates everything.
Happens on both humbuckers.
There is no noise from the amp when turned on and the guitar isn't connected.
Did not happen prior to the setup.

The push pull is pretty underwhelming, I thought about either removing it or changing it to add out of phase in the bridge and split both. I guess it needs to wait until I sort out this thing.

I'll give it a try now, thanks!

ICBM

That probably won’t be necessary now - the ground is well-connected if touching the strings stops the noise.

It sounds like the shielding for the cable to the switch isn’t connected - that’s the connection closest to the camera on the 4-wire connector in the middle. Check that wire isn’t broken, and that it’s pin doesn’t seem loose.

NCo

Do you mean the cable with the broken plastic cover?

ICBM

Yes - that's a piece of sleeving fitted over what is actually a bare wire that grounds the shielding foil inside the grey cable. If that ground connection isn't secure, the guitar will hum and buzz badly when you aren't touching the strings because the roughly 3' of wire between the PCB and the switch then isn't shielded.

Try pulling that wire and see if the pin comes out of the connector, or if it feels broken inside the black sleeving or maybe where it goes up into the grey cable.

NCo

All of those wires are firmly secured into the connector, and the exposed wire doesn't seem to be broken.

After a closer look, that sleeve covering the black wire isn't broken - the edges suggest a perfect cut. It seems as if it was fitted that way, for some reason they left it short?

When moving the grey switch cable the hum intensified, but returned to normal when released.

https://ibb.co/dJsqszZ

ICBM

It will have been cut, when it was fitted - it's put on the bare wire after they strip back the grey outer sleeve, it's not part of the original cable. Left short... bad workmanship! It doesn't actually matter though.

If handling the grey cable adds a lot of noise, it being not grounded correctly is almost certainly the cause.

If you've got a spare guitar string, poke the sharp end of it up into the grey cable just there, so it's definitely touching the bare wire. Then touch the ball end to the back of one of the pots. If that fixes it then the connector is the problem. (You need to handle the string with a cloth or something, or you'll ground it yourself and defeat the purpose of the test.)

NCo

You're amazing mate! That eliminated the hum. Same for when I connect the bare wire to the jack's braided wire. Now should I solder the bare wire to any pot?


I think it touched something else and now when I turn off the amp there's a loud sound, hope I didn't ruin anything it would be comical and the Mrs will kill me if I buy a new amp

ICBM

The loud sound can't be related to the guitar if it happens when you turn off... not sure what that it but let's cross this bridge first .

It does sound like the connector has failed where the shield wire pin connects to it - this could have been caused by the other end of the grey cable (at the switch) being tugged.

The easiest way to fix it is to cut the sleeved black wire at the top of the connector, push the sleeving back up the wire so it touches the grey cable, and then solder the now exposed end of the shield wire to that small spot of solder halfway between the connector and the blue capacitor.

If you don't have a soldering iron, you can do a temporary (but will most likely hold up quite well) fix if you cut a piece of the guitar string, poke one end up the grey cable as before, and poke the other end into the black heatshrink tubing on the jack cable.

NCo

Do you mean this spot? (Red arrow in the image).
Doesn't this mean that the connector will now only have 4 wires going into it?

https://ibb.co/kGQ2XsF

Yea, I am sure it's the amp. The piece of string fell inside and it created a massive pop, ever since when I turn it down (even without a guitar connected) it pops.

ICBM

NCo said:

Do you mean this spot? (Red arrow in the image).
Doesn't this mean that the connector will now only have 3 wires going into it?

Yes. The pin inside the connector should connect to the same copper trace that the spot is on, under the connector, but it seems not to be doing - if you cut the wire and solder it to that spot, you're bypassing the faulty connection in the plastic block. That's essentially what I did with that SG above, except that I did every connection to be on the safe side! Since those plastic connectors are the problem, not the PCB itself.

NCo said:

Yea, I am sure it's the amp. The piece of string fell inside and it created a massive pop, ever since when I turn it down (even without a guitar connected) it pops.

You mean you dropped the piece of string inside the amp?

Oh dear...

NCo

I'll give it a go in the morning, you're amazing, thanks!

No no, string fell on the PCB and created that pop. Even I am not that stupid

ICBM

NCo said:

No no, string fell on the PCB and created that pop. Even I am not that stupid

Not stupid, unlucky .

If it shorted inside the guitar it's hard to see how it could possibly have done any harm to the amp, unless the amp was already faulty and had a voltage leak from the input jack... but that is possible. What type of amp is it?

NCo

First of all, thank you so much, you absolutely smashed it! I may still replace this board, but at least I have a fix which would last, so thank you - bloody brilliant!

I don't think it was faulty before, it's a rather new solid state practice amp I use for low volumes - Orange Crush 35RT. Oddly, when I take out the cable the popping noise isn't there 9 times out of 10/

ICBM

Very strange. If the amp is working normally apart from that I wouldn’t worry about it. Some sort of static discharge when you shorted the guitar probably, but simply turning down the volume pots to zero grounds the output so it couldn’t have done anything else really.

I’ve had to fix a few problems with these PCBs and it’s always the connectors - it’s just identifying which, and what to do about it. I’ve done a couple like that SG where the fault was intermittent and it was just easier and quicker to bypass the whole lot.

I don’t actually think there’s a quality problem with the PCB or the pots, so there’s no real point in replacing them if you can just eliminate the connectors.