Epiphone Les Paul Custom Pro Tone pot issue

[Patriek]

Hi everyone,

 

I love my Epiphone Les Paul Custom Pro, but I noticed some issues with the Push/Pull pots and the wiring. I noticed that the bridge pup sometimes didn't give me any sound. I didn't mind too much, because I like playing on the neck pup more, but after a recent setup (new strings, lowering action, top wrapped), the bridge pup gave issues too.

 

So I opened up the back panel and checked the connections. After wiggling some cables slightly one broke off (see picture)

 

 

 

So I decided to be brave and fix it. And it worked! My bridge pup works like charm again, including the coil splitting functionality of the Push/Pull pot for that pup. At that point the neck pup worked fine too until a day later...

 

 

A day later I found that my neck pup sounded dull/dark/muddy. So, I went out on investigation. After doing a continuity test on the connections everything seems fine (although I am novice to this type of work and I'm not entirely sure how to measure the IC of the Push/Pull pot). I put a little bit of WD40 on the 3-way switch and in the pots, but it did not resolve the issue. After a lot of testing and fiddling, I find that the dull sound of the neck pup goes away when I Pull out the tone pot for the neck pup. The tone pot on this type of guitar adds phase reverse to the neck pup.

 

 

I tested all the connections on that tone pot and they seem solid. I'm now all out of options except bringing it to the luthier. But before I do, I'm hoping that one of you can give me some additional tips that I can try. I came so far, seems like a waste to now have to bring it to the luthier.

[mihcmac]

Hi everyone,

 

A day later I found that my neck pup sounded dull/dark/muddy. So, I went out on investigation. After doing a continuity test on the connections everything seems fine (although I am novice to this type of work and I'm not entirely sure how to measure the IC of the Push/Pull pot). I put a little bit of WD40 on the 3-way switch and in the pots, but it did not resolve the issue. After a lot of testing and fiddling, I find that the dull sound of the neck pup goes away when I Pull out the tone pot for the neck pup. The tone pot on this type of guitar adds phase reverse to the neck pup.

 

 

I tested all the connections on that tone pot and they seem solid. I'm now all out of options except bringing it to the luthier. But before I do, I'm hoping that one of you can give me some additional tips that I can try. I came so far, seems like a waste to now have to bring it to the luthier.

Ok so your Neck and Bridge volume pots do push pull coil tapping shutting down one coil in each pickup providing single coil sound.

 

Your Neck tone pot when pulled reverses the phase wiring of the 2-coils of your neck pickup. When pushed in it should be normal and with the Neck volume control also pushed in both coils should be working.

 

With the pickup selector switch in neck position (Rhythm). If your Neck volume control is pulled out you should get single coil sound, and normal humbucker sound pushed in until you pull the phasing switch on the tone pot.

 

With the pickup selector switch in neck position (Rhythm). If your Neck pickup is muddy, test the volume control push pull to make sure its switching from single coil (cleaner quieter) to double coil (muddier louder) with phasing switch off.

[Patriek]

Ok so your Neck and Bridge volume pots do push pull coil tapping shutting down one coil in each pickup providing single coil sound.

 

That's correct.

 

Your Neck tone pot when pulled reverses the phase wiring of the 2-coils of your neck pickup. When pushed in it should be normal and with the Neck volume control also pushed in both coils should be working.

 

That's correct.

 

 

With the pickup selector switch in neck position (Rhythm). If your Neck volume control is pulled out you should get single coil sound, and normal humbucker sound pushed in until you pull the phasing switch on the tone pot.

 

That's correct.

 

With the pickup selector switch in neck position (Rhythm). If your Neck pickup is muddy, test the volume control push pull to make sure its switching from single coil (cleaner quieter) to double coil (muddier louder) with phasing switch off.

 

I tried this and it seems to be working. There is a subtle difference between when the neck volume pot is pushed in (humbucker) and when it's pulled out (single coil). The difference is subtle, because the volume is very low and the sounds is dull. But the difference is definitely there.

 

 

Do you have tips on how I can measure or test the push/pull pots with these IC's in them? I find a lot of videos on how to do this with regular pots, but not with the pots with IC's.

[Patriek]

UPDATE:

 

Yesterday, I thought of switching the pup connectors to see if there is something wrong with the neck pup, but switching the pups resulted in the neck pup working properly when the switch was set to treble and the bridge pup showcasing the same issue as the neck pup before the switch.

 

So, I can confidently say that the neck pup works fine and my problem probably is caused by the Push/Pull tone pot for the neck pup. Still looking for a good way to test where the issue is exactly in the pot or which connection is faulty.

[mihcmac]

UPDATE:

 

Yesterday, I thought of switching the pup connectors to see if there is something wrong with the neck pup, but switching the pups resulted in the neck pup working properly when the switch was set to treble and the bridge pup showcasing the same issue as the neck pup before the switch.

 

So, I can confidently say that the neck pup works fine and my problem probably is caused by the Push/Pull tone pot for the neck pup. Still looking for a good way to test where the issue is exactly in the pot or which connection is faulty.

 

The Neck pickup being a 4 wire with ground, 2 wires for each coil and a chassis common ground.

 

The Neck tone control phase switch functions by changing how the 2 coils are wired together, from normal in series to parallel out of phase. both coils are used whether in or out of phase.

 

The Neck volume control coil tap switch merely shuts off one coil to give you single coil sound. The problem being the way these controls work, they negate what the other one does. the wiring has to be exactly correct for them to function properly.

 

I could not find a schematic for wiring, but these images for aftermarket LP Custom Pro with coil tap and phase switching harness's may help..

 

 

This link for these harness's may help on pickclick..

[Patriek]

The Neck pickup being a 4 wire with ground, 2 wires for each coil and a chassis common ground.

 

The Neck tone control phase switch functions by changing how the 2 coils are wired together, from normal in series to parallel out of phase. both coils are used whether in or out of phase.

 

The Neck volume control coil tap switch merely shuts off one coil to give you single coil sound. The problem being the way these controls work, they negate what the other one does. the wiring has to be exactly correct for them to function properly.

 

I could not find a schematic for wiring, but these images for aftermarket LP Custom Pro with coil tap and phase switching harness's may help..

 

 

This link for these harness's may help on pickclick..

 

 

Thanks for your explanation. It really helps me to understand what is happening with the wiring. I just think that there is a bad connection somewhere. A couple of weeks ago I heated some solder on the connections and I cleaned (dusted off and scratched the solder between two connections) and the guitar seemed to function correctly again. I was sooooo happy. But now after a week of vacation, I'm running into the same issues again . I think I'm going to rewire the whole damn thing with pots that don't have the ICs in them. That way, I can follow precisely how everything is connected and do the soldering myself.

[Patriek]

UPDATE:

 

After blowing hard over the electronics, suddenly everthing worked again. I'm glad that this is fixed for now (as my new Marshall will be arriving soon ), but I will definitely rewire the whole thing at some point, because this is not a stable situation.

[mihcmac]

UPDATE:

 

After blowing hard over the electronics, suddenly everthing worked again. I'm glad that this is fixed for now (as my new Marshall will be arriving soon ), but I will definitely rewire the whole thing at some point, because this is not a stable situation.

 

Humidity, corrosion or oxidation on the connectors could be factor, if blowing on it or reseating the connections got it working again.. Glad you got it working... Enjoy...