Hi Just discovered this forum while trawling for some information on what the innards of an Epi SG copy ought to look like...
I'm hoping that maybe somebody here will have a better idea of what is going on inside this guitar and be kind enough to explain it to me, because it doesn't match up to anything that I have found so far.
If I had a camera I would post a photo, but I'm afraid a drawing is the best I can provide.
I picked up the guitar at a car boot sale, and I'm pretty sure it has been... "reworked" at some point in its life.
I couldn't draw the white wires as white, so used a light blue instead I hope that's ok.
It came with a gig bag that had a label for a Kent Armstrong pickup in it, so I'm guessing that at least one of the pickups won't be original.
If anybod can shed any light on this I would be very grateful.
The diagram you posted is the standard SG or LP wiring scheme, where each pickup gets its own volume and tone control. The diagram doesn't show the grounds all being connected together, however. This could be done by running a ground wire (often done with bare wires in guitars)from pot to pot, and then to the switch ground, which is then connected to the output jack sleeve.
It is also possible the the pots and switch are all grounded together through contact with shielding or conductive paint in the cavity.
This works as follows: Each pickup is wired, first, to its volume control. The "hot" wire from the pickup goes to the center "wiper" lug of its volume pot. The other two wires from the pickup, the gray wires, represent the ground and shield wires, which are soldered to the back of the pots.
The tone controls are then wired in parallel to the volume controls.
The output from each volume pot (the lower lug of each, as shown)is then wired to the three-way pickup selector switch, which is in turn wired to the output jack.
That's a pretty simplified explanation, so I suspect you will have more detailed questions.
I have googled LP schemes, and have managed to achieve a state of confusion regarding the "modern" and "50s" wiring. The confusion is caused mostly by people arguing the merits of the two - the layouts are clear. Most people seem to agree that "50s" is better... if so why have gibson stuck with "modern" for over half a century? There doesn't seem to be a cost difference between the two... Sorry, that's off topic, ignore that!!
My biggest mystery on the wiring in this guitar is the extra wires coming from the bridge pup. They don't crop up on any of the LP/SG schemes that I have found so far. I don't know what they are for. I can guess... coil split? But with one of them grounded and the other one taped back on the cable I can't see how they can be doing anything?
There is a fault on the guitar, it varies in volume and tone without touching the controls so I am going to have to grab a soldering iron and have a go... I could just buy new pots and resolder everything as it is now, but with those extra wires and their function and locations confusing me I am nervous about replicating a wiring mistake!
As far as the bridge humbucker goes, you're right, the extra wires are for the coil split. Someone replaced the bridge pickup at some point, in all likelihood.
Now, a bit of discussion of this. Humbuckers usually have their two coils connected in series, so the end of one coil is connected to the start of the other, leaving two wires coming out of the pickup for wiring to + and -. Older humbuckers made this intra-coil connection internally- we'll call these two wires tied together the "series junction" of the two coils of the HB. So, as shown for your neck HB, there are only two wires(plus a shield wire for grounding the frame of the pickup). On these older HBs, the coils cannot be split, unless one does major surgery to the pickup to disconnect the series junction and run separate wires out.
Aftermarket pickup manufacturers wanted to make it easy for people to do alternative wirings, including splitting the coils of the HB, and so began to offer "4-wire humbuckers", so that each coil can be independently wired. This allows for the two coils to be split, or to be wired in parallel or out-of-phase as well. These modern 4-wire HBs also usually have a separate shield wire (commonly a bare or braided wire), so there's actually a total of 5 wires.
But, if one doesn't wish to do those alternate wirings, and just wants an ordinary HB, then two of the four wires are joined together outside of the pickup to form the "series junction", just as is done internally in the old-style HBs.
There is also a third type of HB, called a "three-wire" HB. These also often have a separate bare shield wire, and so there's actually 4 wires, but it's understood that the shield is always grounded and doesn't carry any signal from the coils. So, just as with the 4-wire type, we omit the shield when we speak of how many wires it has- we're talking only about the signal-carrying wires.
On the three wire types, the series junction is internal like on the old-style HBs, but a single wire runs from the series junction out of the pickup. This third wire allows for coil-splitting, but that's all. The coils cannot be fully independently wired as on the 4-wire type. They cannot, for example, be wired in parallel.
On the three-wire HBs, if one is not using the third wire to split the coils, it is left disconnected and taped off, leaving the internal "series junction connected together.
On your diagram, it would appear that you have a three-wire HB for the bridge, unless what you show as one wire being taped off is actually two wires together. I see a green ground wire and a separate shield wire soldered to the back of the pot (which, as above, we don't count). I see an orange wire running to the Volume pot "Hot" for the output. And I see one wire taped off and not used. So, three signal-carrying wires, with one taped off and not used, since there's no coil-splitting going on.
Again, if what you show as one wire is actually two together, then it's a 4-wire HB, but everything else I said still applies.
As far as your intermittent loss of volume, that would indicate a bad connection somewhere. Intermittent problems are the worst to track down and fix, since the state of the guitar keeps changing.
The diagram looks like it has the dreadful 'independent wiring', aimed at preventing one volume control turning down the whole guitar when both are selected, but actually messing with the tone quite considerably . The pickups are going to the volume pot centre lugs, whereas they normally go to the outer lugs. Normal wiring is much better. That's different issues to 50's v modern, which is to do with the tone pots.
Are the four bridge wires similar in thickness, all insulated? in which case it looks like 4 conductor wiring of that pickup, plus the braid being for ground. But I don't recognise the combination of colours.
I suggest it needs a do-over, but first use a meter and tap tests to figure out the bridge pickup. Also, any circuit where an important wire connection is held on by tape needs to be started again from scratch IMO
Well, based on what's been said here I picked away at the tape holding the wire to the cable, and the mystery has deepened...
The tape was concealing another wire. so, to summarise:
There are four conductors from the bridge pickup, in addition to the braided shield.
I must apologise for the colours on the diagram. The four conductors coming from the bridge pup are: RED - soldered to vol pot middle lug. (this is orange in the picture) WHITE - soldered to the previously concealed BLACK conductor and taped to the cable jacket. GREEN - soldered to the back of the volume pot, as is the braided shield.
With regard to the "independent" volume controls...
With the switch in the middle position turning down the neck vol all the way kills all the sound. Turing the neck vol back up and turning the bridge vol all the way down kills just the bridge pickup. If you turn down the bridge vol all the way, "neck" and "middle" positions on the selector switch are essentially the same!
I don't know what is going on...
I don't have a camera, but I'll try and borrow one tomorrow from one of the guys at work... If you saw the inside of this thing I'm sure everybody would be jumping to "bad solder joint" as the cause of the intermittent drops in sound... blobs of solder everywhere and lots of dirt in there... no backplate on the guitar and I think it has been missing for years!!
When it's working the sound is great, so I would be happy to rewire it with new pots and reconnect everything the way it is now... But I don't want to do that if it will be making things unsafe.
I'd also genuinely like to understand what's going on in this... I can borrow a digital multimeter from work. If anybody can suggest what I should check first and what readings I should expect to see I would be very grateful.
My instinct is to figure out the bridge pup first, maybe take a reading from the green wire to the red wire. Not sure where to proceed from there... maybe split the white and black wires, and read from the red to black. I would expect red to white to read the same as red to black?
In an ideal world my learning on this wouldn't be starting with a second hand rewired guitar with unidintified pickups and dodgy soldering, but since this is where I am and what I have to learn with I will welcome any help, information and advice that people here are prepared to offer!!
Now the wire colours match the colours used by Kent Armstrong - at least according to that page. Their instructions are to solder Red and Green together, ground White and send Black to the volume control.
This implies that Red and Green are that "series junction".
As it's wired in this guitar Black and White are soldered together...
Now bear with me, because as I said I'm trying to learn as I go here...
My brain is telling me that for the coils to be wired parallel I would have to see two of the wires grounded and two going to the volume pot, and that's not happening here.
My brain is also telling me that I must have coils wired in series because I still have a "series junction", although it's the "wrong" one according to the sheet...
So what do I actually have? Could this be the mysterious "out of phase" that I hear whispered about in hushed tones? Or is this unlikely to be any different from joining red and green as per the Kent Armstrong page?
OK, there's a lot in there- let me try to break this down.
Your HB is wired "inside out" as compared to the KA instructions. It will sound exactly the same as if it were wired the "right way around" as per the instructions.
Their instructions are to solder Red and Green together, ground White and send Black to the volume control.
This implies that Red and Green are that "series junction".
Yes, exactly. But we can also wire the pickup "inside out". To do so, the black and white become the "series junction", and the red goes to the volume pot, green to ground. The two coils are still in phase with each other, and will sound identical to wiring them the stanbdard way.
There are reasons to wire HB coils "inside out", mainly so as to select the other coil when splitting coils. For hum-cancelling (when in combination with another SC) it matters which of the two HB coils is the one which is operational. In you guitar at issue here, it doesn't really matter, since there's no coil splitting going on (at least, not yet . . . )
The HB coils are not in parallel here, they are in series as is the usual way of wiring HBs. As I noted above, in the old days, that was the only way to wire them, without major surgery to access the internal "series junction".
Out of Phase (OOP) is a whole topic unto itself. In the example above, if you were to swap the wires of one coil around, while leaving the other coil "as is", the two coils would then be OOP with respect to each other. OOP can be useful sometimes, when it is between two different pickups. But putting the two coils of a HB OOP with each other generally won't give you a useable sound. The coils are too close together and too similar to each other, so more frequencies cancel out when OOP, leaving only a tinny, low output signal.
I like your detective work to figure it's a KA pickup, and you're probably right. However, if it's not one, it may have a different color scheme than what we're assuming here. But it doesn't really matter unless you're planning to disconnect the series junction for other wiring options.