Electrical hiccup

[Olddon]

I recently bought an SG style DIY kit and finished it a few days ago. It was prewired with two vols, two tones and a three position selector switch. I noticed that while both pickups worked only one was working in the centre position. A bit more investigation left me totally confused. With the selector switch in the centre position only one pickup is working (say the front). If I then turn both volumes to zero and turn the front volume up again nothing happens but the rear pickup is now working. I can go backward and forwards between the two pickups like this, but never both together 🙃

Any ideas or suggestions?

Thanks
Don

[Simon Barden]

It sounds like they've miswired the circuit to me, or else there's a broken connection.

Can you post pics of the wiring that clearly show the overall wiring and the wiring on each pot (move wires out the way if necessary so we can see the connections to the pot connection tabs).

[Olddon]

Thanks. Will do. Its a bit late here in the Antipodes but I will put them up tomorrow.

[Simon Barden]

I suppose you have fitted the pots the correct way and wired the pickups to the appropriate pots with the bottom 'front' (nearest the neck) being bridge volume, bottom rear being bridge tone, top front being neck volume and top rear being neck tone.

I've connected up the pickups the wrong way round before on a LP copy.

[Olddon]

The pots are all in the correct positions, after my second set up , and the wiring was all prewired, pre soldered so all I had to do was attach the controls (pots, switch and plug) and connect the PU's. Just a push together plug. I have had a close look and to my untutored eye it seems ok, but again I don't know what should be connected to what. There are however no loose wires.



Hope this is of some help.

[DrNomis_44]

Olddon, I think I might have a circuit diagram for a Les Paul, or SG in amongst the circuit diagrams in my Dan Erlewine Guitar Player Repair Guide book, I'll see if I can find it and post a pic of it here for you.


Here we go, this schematic is for a Les Paul but the SG uses the same exact schematic, hope it proves useful in sorting out your SG build:




Note that most Les Pauls and SGs these days use a .047uF, or 47nF tone cap instead of the .022uF or 22nF shown in this schematic.

[Olddon]

Thanks Dr. I’ll sit down tomorrow with a magnifying glass and see if I can match the spaghetti in my guitar with your diagram 😳. Cheers

[Simon Barden]

I'd ideally like some more photos. You've got wires covering up a lot of the pot connections, so I can't be 100% sure of everything. It generally looks OK, but there may be something hidden that's not right.

The bridge tone pot capacitor legs look like they might be touching each other. Definitely move the cap so the legs are separated (check on both tone caps).

I'm not 100% sure the neck volume pot has the lowest tab in the photo folded back and soldered to the casing properly.

It would have helped if they'd stuck to a decent colouring choice for the wires e.g. all grounds black, all bridge signals white and all neck signals red, with the common output blue. Then it makes it much easier to follow the wires.

But as I've said, there are still wires covering up a lot of the pot connections. You may have to take photos of the individual volume pots (the tone pots look OK apart from possible shorts between the capacitor legs).

[Olddon]

Dr, I have checked my wiring against your diagram and all seems good.

Simon please find enclosed another couple of photos. I have checked the potential problem area's you mentioned and they all seem fine. The fact that the symptoms change after both volumes have been set to zero makes me think it is more an electronics problem than an electrical problem. If that makes sense.

[DrNomis_44]

Dr, I have checked my wiring against your diagram and all seems good.

Simon please find enclosed another couple of photos. I have checked the potential problem area's you mentioned and they all seem fine. The fact that the symptoms change after both volumes have been set to zero makes me think it is more an electronics problem than an electrical problem. If that makes sense.

It's possible that the volume pot for the non-working pickup might have a loose solder lug on it, by loose I mean that it's not making proper contact with the carbon track inside the pot, you can check that by gently wiggling the solder lugs with a finger, they should not feel loose, if one does feel a bit loose then you'll most likely have found the cause, sometimes pots develop loose solder lugs if too much heat is applied when soldering the connections, I've had that happen to me a few times.

Those 16mm pots are notorious for developing loose solder lugs when they get a bit overheated, I've found that strangely, some pot values seem to be more prone to it than others.


If you feel like upgrading to some better quality pots, you can order 500kA CTS pots from Realtone Music, here's a link to the website:

www.realparts.com.au