Electrical hiccup

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

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).

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

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.

The pots are all in the correct positions, after my second set up :D, 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.

Attachment 43740

Hope this is of some help.

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:

Attachment 43741


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.

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

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).

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.


Attachment 43742

Attachment 43743

Quote:

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Originally Posted by 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.


Attachment 43742

Attachment 43743

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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

Yes, Doc, it could be that heat has damaged the carbon track inside one or both of the volume pots. That can lead to some strange behaviour.

There is nothing active in this guitar's wiring, so its all electrical, not really electronics.

From the photos I'm still not 100% convinced about the solder connections to the bent pot lugs. I'd reflow them with fresh solder if it was mine. And the solder blob on the back of the volume pot in the lower of the two photos doesn't look great. Another join I'd redo. Lead-free solder needs to get hotter than leaded solder to melt and flow well, so it's not easy to solder to the back of a pot.

If you look at the second photo, the solder blob on the left has a rounded top and flows onto the rear of the pot. But the solder blob on the right with more wires is more of a round blob. This can mean a poor join, where the solder is lightly tacked on rather than making a solid connection throughout.

It could be a combination of things.

Are you familiar with Gibson-style 2 x volume 2 x tone controls?

If not, you may not be aware that with both pickups selected, if you turn one pickup off, you get no sound at all from either pickup.
Some people thing this is a problem when it's just the way the circuit was designed. The output of the volume pot is taken to ground when the volume is at 0, and as the two pickup outputs are connected together when the selector switch is in the middle position, the second pickup's output is also taken to ground, so no sound. It's one reason you have a selector switch (to isolate the output of one pickup from the other), otherwise you could just use the volume controls.

Thank you very much for the info and the for the link. I am off to do some wiggling 😬

Assuming you may end up changing the pots, you should note that with CTS pots, you'll probably need to get new control knobs as well. Pot shafts come either with 18 spline or 24 spline shafts. The kit ones and any Asian-made pot will invariably come with 18-spline shafts. American CTS and Bourns pots normally come with 24-spline shafts, and knobs designed for one type of shaft won't fit on the other. You can get 18-spline versions of Bourns and CTS pots but they aren't generally held in stock by a lot of suppliers. Alpha are just as good pots and again can be had in 18 and 24 spline versions, but I think the default is 18 spline.

Pots also come in short shaft (~6mm for scratchplate mounting), medium shaft (9-10mm for rear-routed cavity guitars) and long shaft (~19mm for guitars with really thick tops and shallow cavities) lengths. You'll want medium shaft lengths for your SG kit.

Pots also come in two collar sizes, M8 (generally found on Asian-made pots, especially kit ones) and the larger 3/8" (generally US-made pots or ones designed as replacements for them). Your kit probably has the 8mm holes which will need enlarging slightly to fit CTS or equivalent) pots. I use a hand reamer for this, rather than a drill.

And I'd get audio taper pots for volume and tone. Your kit uses linear for volume and audio/log for tone. Linear for volume gives you almost on/off control with clean sounds, so audio taper for volume is always recommended. Tone is more a preference for how you like the tone control to act, but I prefer audio taper for that as well as you get control over a wider range of the pot travel.

My Steinberger Spirit GT Pro Deluxe headless guitar, which I bought on eBay, originally came with two 500k B (linear) 16mm pots factory installed, the one that was the master volume felt a bit gritty and sounded a bit scratchy, I tried spraying it with some electrical clean and lube but that didn't fix it, so I ended up replacing both of the pots with two new 500k A (log) 24mm CTS pots I ordered from Realtone Music, as Simon said, I had to enlarge the two mounting holes before I could install them, anyway, once all the re-wiring had been done I tried out the guitar and if my ears weren't lying to me, I noticed a definite improvement in the overall sound of the guitar, not sure why, but I definitely could hear a distinct improvement in the tone.

Guys, I am feeling really really embarassed. As Simon asked earlier 'was I familiar with the Gibson style set-up with volumes' and no I wasn't. When I went back and tried a bit harder I realised that both PU's are working in the centre position. I have some good rationalizations ready to roll, but they are just fanct excuses.
On the bright side I have learnt a lot about pots, splines, mounting holes, things I wasn't aware of before and will come in useful. I also took the opportunity while the wiring was exposed to solder in a pure tone output jack to facilitate my 'not so pure' playing.
The result, while working, was not beautiful and along with some burnt fingertips I realize I need more soldering practice before starting on my TL kit.
Thanks again for your help.

Doc, it was probably down to a better overall ground connection after you soldered the pots yourself. Even cheap mini pots make a good circuit connection at full volume, where the input and output are shorted together.

Glad you got it all sorted, Olddon.

Changing to a Pure Tone jack is a good move, it’s all I use these days.

And soldering practice is always useful and never wasted.

Quote:

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Originally Posted by Simon Barden

Glad you got it all sorted, Olddon.

Changing to a Pure Tone jack is a good move, it’s all I use these days.

And soldering practice is always useful and never wasted.

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Yes! I recently bought a dozen Pure Tones (one for each guitar :o). Got a very good price for them by AUS standards.
I've only replaced the Switchcraft ones in 3 guitars so far. Will work through them all eventually as they end up on the bench for various other maintenance items.

Quote:

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Originally Posted by Simon Barden

Doc, it was probably down to a better overall ground connection after you soldered the pots yourself. Even cheap mini pots make a good circuit connection at full volume, where the input and output are shorted together.

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You could be right, the passive pickup wiring systems commonly used in most electric guitars are high-impedance circuits, so I guess making sure the ground connections in them are good is essential to get the best tone out of them, if my ears aren't lying to me, I swear I can hear a difference in tone between a 500k B pot and a 500k A pot, the 500k B pot seems to sound slightly harsh to my ears, and a 500k A pot seems to have a smoother overall tone that sounds more "musical" to my ears, the difference between a 500k B and a 500k A pot is that a B type pot is linear whereas an A type pot is logarithmic and more or less matches the response of the human ears, both are 500k pots so you'd think that they would "sound" the same, but to my ears the A type pot seems to sound sweeter for a lack of a better word, my theory anyway.


And yes, I agree, those Pure Tone 1/4 inch jacks are great, they are a big improvement over the standard ones since the Pure Tone jacks feature two contacts for the ground or sleeve connection and two for the tip connection for more positive contacts, I definitely highly recommend buying them, I've got one installed in my Mexican Telecaster, works great, I'll definitely buy more of them.

Hey just throught I'd throw something simple out there.

I doubt this to be relevant to your situation, but I've had a similar problem that I just could not figure out... I suspected a loose solder joint somewhere but I went over every joint and it wasn't that.

Turns out I'd over-tightened the nuts holding one of the pots in and it didn't like it. Loosened the nut on the problem pot and that resolved the issue.

As I said, probably one in a million for that to have been the problem, but it's free and easy to test.

Failing that, I'd suggest finding a multimeter to start testing continuity, while following the wiring diagram, that the good doctor provided above.

Quote:

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Originally Posted by D3210210

Hey just throught I'd throw something simple out there.

I doubt this to be relevant to your situation, but I've had a similar problem that I just could not figure out... I suspected a loose solder joint somewhere but I went over every joint and it wasn't that.

Turns out I'd over-tightened the nuts holding one of the pots in and it didn't like it. Loosened the nut on the problem pot and that resolved the issue.

As I said, probably one in a million for that to have been the problem, but it's free and easy to test.

Failing that, I'd suggest finding a multimeter to start testing continuity, while following the wiring diagram, that the good doctor provided above.

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I've been there and done it too, it's a very easy mistake to make, overtightening the mounting nut for the pots, I seem to remember doing that once and ruining a perfectly good pot, I also seem to remember muttering some pretty "colourful" words after I had realized what I had done too, complete with feelings of utter embarrassment.

Hi All, Did you know that Kronig Supply are the Pure Tone exclusive distributor in Australia / NZ. We keep every model of PureTone jacks onshore in Sydney including barrel and panel mount. Also, spare nuts (if you need them to adjust the protrusion). Ask your local guitar shop to contact us and we can ship them usually same business day.

P.S. Let me know if we are not allowed an "advertising post" but I feel it is in the interests of members to know that they don't have to wait for overseas shipments of PureTone (and SquarePlug, and G&H)