Maxon humbucker repair
I was getting some guitars ready to take to the shop and pulled out this '73 Greco LP for a quick clean and set up. The guitar itself is in pretty good condition but when I plugged it in, no sound from the bridge pickup?
I usually start by cleaning out all the pots, the switch and the jack as time can corrode these and make bad contact for the signal to pas through. In this case, this still didn't get any noise from that pickup. I took the back plate off to check the wiring and measure the pickups.
There it was. No resistance at all from the bridge pickup. The neck was reading a healthy 8.5K so I unsoldered the wires from the pot and measured again. Still nothing. I thought I was going to have to fire up the winder?
These early Maxon made pickups have a tendency to break where the lead wires attach to the coil so all wasn't lost just yet.
Now, you have to be REALLY careful pulling old pickups apart as I've seen almost as many pickups destroyed and need a rewind from careless disassembly, than manufacturers bad quality control. They are delicate and this just proves that they can be salvaged if you take care and understand what's going on.
These early HBs didn't have the covers soldered on like Gibson and later Maxon ones but are instead just glued on. Carefully run a blade down each side of the cover between the base plate and the cover. You should be able to pull these free from the cover now. If it's still a little sticky, try some heat from your soldering iron to soften the glue.
Now you have access to the lead wires at their ends. Take measurements from each coil to see which one, or if both are dead. In this case both were ready zero.
Carefully unsolder the shielded lead wire from the pickup and remove the coils. In this case the coils are on plastic (or nylon) bobbins glued around the poles in each side. The bobbins should just slide up and out but don't pull them too vigorously as you'll pull wires out completely.
With both coils out take the insulation off the pairs and unsolder the wires so you have two completely separate bobbins. Now measure each coil again. Still nothing.
Carefully unwrap the tape from the coil. Here's where you can break a good coil if you're not careful. This tape, especially on lots of old Japanese pickups can be very tacky, and fragile so take your time. If you break the magnet wire from the start of the coil here, it's a rewind, even if the coil is intact so be careful.
Once you have the tape off see if the smaller inner lead wires are still attached to the magnet wire. In this case they have not used the small holes in the bobbins to locate these wires, which could be part of the reason this happened. The magnet wire is no thicker than your hair so you'll need to look carefully. Draw or take photos to remind yourself when you're reassembling what wires went where and what colour they were. Believe me, it'll help when you're half way through and someone knocks on the door and when you come back you can't remember.
In this case (and other Maxons I've seen) these wire had broken off the magnet wire and were just held in place with the tape. It was the same issue with both coils so next we find the start and finish of each coil and carefully (there's that word again) clean the ends of the magnet wires so we can solder to them. The start of the coil will be the one coming from "inside" the coil so we need to be VERY careful not to damage or break that as we can't unwind more from that end.
Once you've cleaned each end of the coil use some light wet and dry paper to remove the insulation from the magnet wire. You only need enough to solder to so maybe 5-10mm max. Once this is removed you can reattach the inner lead wires to the coils.
Measure the ends of these wires to make sure you still have continuity and carefully reassemble the coils with new tape to keep everything tight and secure. You can sometimes use the original tape (if it's usable and a rare pickup) but almost always use new fresh tape to make sure it's not going to fall apart again.
With both cols done reference you drawing or pics and reassemble the coils the same way you pulled them apart. If you didn't mark it down, don't stress as you can, through trial an error make it work as long as both coils are working. You can change start/end inner leads to get the pickup back to a humbucker and make sure it's in phase with the other one in the guitar. It's just easier if you marked it down as you'll get it first go.
Once the pickup is all soldered and in phase, replace the cover and glue it back in place.
This is not a difficult job. It can be time consuming and tedious but with patience and a soldering iron you can fix a pickup that has failed in this way if your .... yep, careful.