In/out phase pull/push pot gone AWOL

[Jazz Rock]

So I finaly put back the Epi together but I haven't done a great job of it - Looking good though!

I came up with the below wiring to achieve in and out of phase mod and a kill switch with the push/pull pots, with the 50's wiring for the caps 5turns out I already installed them like this before so didn't move them as I liked the way the volume pots behaved).

The kill switch works a treat. But when I plugged in the guitar, 3-way switch in the middle position, I was surprised that there was not much of a drop in level between the in and out of phase positions... and then I realised that the bridge pup was silent. I suspect it is a grounding issue.

I have made the connections almost exactly as per my schematic, apart from the fact I haven't linked the grounding of the bridge pot to the rest of the grounding network, which all comes back to the volume pot of the neck pickup. I was thinking that could be the problem, but then I remembered that it was wired like this before and I didn't have any issue before... At least I am pretty sure it was. I don't think I have a photo I could check though... Anyway, the main alteration to the circuit from it was before I installed the MQs is the kill switch, but this works fine, and the in / out of phase mod... and my guess is it is the latter I messed up.

I have taken a photo of the control cavity before closing it off, but I had to have some of the wires go round the cavity because they were quite long, so it is not easy to see excatly what goes where. I'll take a picture of the connection to the push/pull later, it might help you spot the mistake... assuming my wiring diagram is not the problem.

So let's have it, what is your diagnostic?

[Jazz Rock]

Seriously guys! Noy even a single wee suggestion??? You wouldn't want a Mississippi Queen set to be wasted  PDT_039

[Jazz Rock]

Ok guys,

Managed to sort out the silent bridge pup. It was indeed this missing ground connection between the bridge volume pot and the main grounding point.

Nonetheless, in my initial disappointment, I hadn't realised how much static the guitar was producing. Having solved the original issue, I have tested the guitar with my small amplug, and then the Tweaker, the hum is stronger than the main signal, which is a real shame as the sound of the pups is quite good if you try to ignore the hum (which is quite a mental prowess as it is so loud - not to be attempted on long period of time).

I did a bit of a search on different forum, and I am wondering if the next step would not be getting some foil tape to the cavity cover and solder a wire to it from the main grounding point. What do you say? Do you think it would help? or is there something else I should try?

[Jazz Rock]

I have spent most of my Saturday trying to sort out the Epiphone and despite all the time and efforts, I am only very marginally better off than I was on Friday night: The static noise is now half as loud as the signal, Which is really a shame, because suring the tests, I could here good the pups are sounding.

So I have tried quite a few things:

Because the noise reduces dramatically when the tone pots are rolled all the way back off to 0, I thought there might something funny with the way I connected the volume and tone pots. I was using the 50's mod, so thought that it might be more prone to hums, which could be why the modern way came about. I have tried what you would call the standard wiring, as well as the Black Rose Custom... It didn't have any affect on the hum.

Following advice from shag101 via PM, I wired the bridge pup directly to the jack, white wire to the wire I disconnected from the kill switch, so almost as direct as it will get, but I wired the black and bare wire to the grounding at the back of the neck volume pot, not directly to the ground lug of the jack. The hum was still there, so I am not sure if the issue is with the pups or with my grounding... I would tend to think it is more likely my wiring, but I have fired of an e-mail to Tim to have his opinion.

I have also applied foil tape to the back of the cavity control cover and soldered a ground connection to it, but it didn't seem to have any affect either.

Finally, I have re-soldered some of the grounding connections, those that seemed like they could be at fault, but still nada...


Those of you who followed my ordeal with putting back up together this guitar, will remember that I potentially have overcooked some of the pots. So I am also wondering if this coul dbe part of the issue, espacially as the volume pot work more like on/off switches then gradual pots. About everything that could have gone wrong has!

So unless Tim comes back to me saying the issue may be with the pups, which I doubt, I think the way forward is to gut the guitar and start again from scratch. But if I do this, I wonder if I should change the pots in the process. My Gibson has a metal plate to which all the long shaft pots, are connected, would it make sens to introduce one in the Epiphone. At the moment th epots are dirctly fixed to the maple top, and that's it. It may be tricky to find a plate with all cut to Epiphone's dimension, and I am not equiped to make one myself.

I thought I would just post about the "Saturday experience" as it might give enough information for one of you to find what I am doing wrong. I'll go for a quick hunt on the web now to see if there are any plate kicking around.

[Transcend]

Have you checked your output jack?

My RGD developed a lot of hum the other day and it was the ground from the ouput jack was only connected by a few strands.

[Jazz Rock]

Hey Toe-knee,

I have redone all the connection to the jack, so they should be ok. Nonetheless, I have altered most of the wiring, thinking I was doing a serious enough job... Yet it does nae work so there must be a bad connection somewhere, unless one of the components is faulty. Can the jack be damaged by excessively long exposure to heat, like when I was having trouble with the soldering iron when I started working on the guitar?

[Shag101]

The pots could be shot from the heat, but if you hooked the bridge up directly to the output jack, thus bypassing all the pots, then I doubt they are the main issue.  I would still replace them as you mentioned they do not work properly. 

Do you get any difference touching or not touching the strings?

You mentioned in a PM that the hum goes away in another room?......yet your MQ neck in another guitar does not feedback anywhere.

Would be a lot of work, but I wonder if you put your MQ neck that does not feedback into the epiphone, would it feedback..and visa versa with the pup that gives feedback..
It would pin down the problem area...

[Jazz Rock]

Messing with teh Studio will be a last resort solution, it is working so nicely that I wouldn't to screw this one up as well...

As far as string touching is concerned, it odesn't really have much effect. It does attenuate or mute very slightly the hum, but which it is going to do is function of how is the guitar orientated in relation to the amp.

I think I'll take everything in cavity out at the week end. I would quite like to find a metal plate like there is in my Gibson, I am sure it could help with grounding issues. I don't seem to be able to find a place that sell them... maybe it is something someone from the forum could supply?!?