Ancient Rotary Switching Wiring Confusion - Help!

HarrySeven

I've just started working on an old Musima. Unfortunately, in the distant past, some bright spark disconnected everything and left it in a bit of a mess...

Essentially, what you have are two pickups (Neck - single core & GND and Bridge - 2 core & GND) which both work, a rotary switch and a pot.

Rotary switches confuse the hell out of me, so any advice would be greatly appreciated. I've drawn out the schematic (or at least, what's left of it).

Any advice would be greatly appreciated!

ICBM

Yikes! I will have to think hard about that one. It can be done, just give me a bit of time .

I'm assuming the four selections are pickup 1, pickup 2, both pickups series, both pickups parallel. That can be done if one of the pickups has 2-conductor+shield cable, so it fits.

I also assume the terminal with the white wire goes to the centre hub on the bottom layer in the same way as the one with the yellow one wrapped around it does on the top, or it won't work.

HarrySeven

Most of the wiring that's still there looks original, so fingers crossed, it's just a case of hooking up the pickups and outputs...

I'll have a closer look later, but I'll work on the premise that the majority is original.

ICBM

HarrySeven said:

Most of the wiring that's still there looks original, so fingers crossed, it's just a case of hooking up the pickups and outputs...

I'll have a closer look later, but I'll work on the premise that the majority is original.

Yes, it does look like it - the maroon cloth tubing all looks original and undisturbed, which is a huge help.

HarrySeven

When I'm back at my workbench, I'll take a close look at the solder joints and see if there are any obvious signs of reworking.

HarrySeven

Updated:




All joints seem quite old and having looked very carefully, I can confirm that the linked centre hub/first terminal on the left is duplicated on the bottom layer.

HarrySeven

Another update. Unless, I'm completely stupid (which I might be), the outputs should be:

ICBM

You've got the connections on the volume pot round the wrong way (output is correct, the other two are reversed), unless the volume pot is meant to work backwards!

But the switch wiring does make sense - if the three wires on the left of your drawing are, from left to right: pickup 1 green wire, pickup 2 white wire, pickup 1 black wire.

Position 1: green wire grounded, black wire already connected to volume, white to empty terminal - pickup 1 on.
Position 2: green wire to empty terminal, black wire to volume (but does nothing since the green wire isn't connected), white wire to volume - pickup 2 on
Position 3: green wire to white wire, black wire to volume - both pickups in series
Position 4: green wire to ground, white wire to volume, black wire to volume - both pickups in parallel

The link between Top 2 and Bottom 1 seems unnecessary, but may be to prevent switching noise - or may not be original, since it's bare wire.

HarrySeven

Well spotted - thank you!

Here's the revised version - I think that's correct now?

ICBM

Yes, I think that should work!

HarrySeven

I'll tackle it ASAP and let you know!

paulnb57

This forum really is pretty awesome! Great to see folk helping each other out....

HarrySeven

And now for the fun bit...as you can see, the pickups have rather short cables, so some new braided stuff is the order of the day.

However, I imagine that getting it through the body will be entertaining...some nice 90-degree angles to deal with!

paulnb57

I thought access on my Epi 335 was a struggle, good luck!

normula1

try a stiff-ish piece of solid core wire e.g. earth wire from some 6A lighting wire or maybe a long cable tie if the holes are large enough 

ICBM

Yes, I would use a long piece of stiff solid copper wire bent into a hook about half an inch wide at the far end, poke it through from the control cavity to beyond the pickup wire holes, then put the pickup wires down the holes, then pull back. That should catch the wires and pull them through to the cavity, but they will definitely need to be longer than the bare minimum or they'll slip out of the hook.

HarrySeven

Well, after over an hour of wrestling, I'm at this point...





Jeez, what a PITA!  

paulnb57

Youve broken the back of it now!......Finished by close of play today?.........

ICBM

Make sure you solder the pickup wires to the ends of those before you try to pull them through, not just tape and/or twist them together - it's tempting to think they can't pull apart when they're twisted and taped, but experience proves otherwise!

paulnb57

Cracking idea to solder them, Wisdom!