Testing coil split wiring without disassembly

digitalkettle

I have a two humbucker guitar which are both coil split but I'm not hearing an audible effect when splitting the neck pickup.

Does it prove anything to measure resistance across the guitar's output while changing the switch position?

Pickup selector to bridge gave 5260 ohms (unsplit) and 2649 (split)
Pickup selector to neck gave 2306 ohms (unsplit) and 2275 (split)

I'm sure that's a bit coarse but the bridge results make sense to me and the neck results show barely any change.

Alegree

You've got something going wrong there. No humbuckers are 5.3k. Are all your controls maxed for testing?

digitalkettle

Yep, controls maxed (I'll check again).

They're actually Haussel Tronebuckers, if that makes any difference.

Alegree

Humbuckers are typically 7-20k. I can only see those readings with a split/parallel which goes from 1/2 to 1/4 resistance - so your humbucker would be 10k in the bridge. That would be a normal reading for standard operation.

digitalkettle

Thanks @Alegree ;

Readings aside, does my approach seem sound? I should expect the neck resistance reading to half when split...just like the bridge does?

Alegree

Yes.

ICBM

Unless it has a resistor in series to give a partial coil split, like PRS uses on the DGT. In that case you will get the combined resistance of one coil plus the split resistor, which could be in the range you're getting. If the switch wasn't working at all you would get no change.

What happens if you tap the polepieces with a screwdriver when the pickup is split - do you get a different noise on each coil? (ie the sound through the amp!) Is it different from when the pickup isn't split?

digitalkettle

Bridge behaves as you'd expect but the neck polepieces sound the same whether coil tapped or not.

ICBM

In that case it sounds like the switch may have a bad contact in it, if the resistance changes a bit but one set of poles doesn't go quiet.

digitalkettle

Thanks...I'll look into it.

digitalkettle

This is weird...it's 'fixed itself'...all on its own

Pickup selector to bridge reads 5270 ohms (unsplit) and 2650 (split) [same as before, more or less]
Pickup selector to neck now reads 4440 ohms (unsplit) and 2279 (split)

I haven't sprayed any contact cleaner or taken anything apart...although I have done quite a bit of staring at it. So I presume a bit of usage (it's a new guitar) has 'freed up' the push/pull pot...and the neck pickup was permanently split up to this point?

digitalkettle

Goddamn...I just tried it again and it's back to faulty! Multimeter back into action...

Pickup selector to neck gave 2348 ohms (unsplit) and 2300 (split)

Very slightly higher readings than last time...and I'm sure it varied a little as I wobbled the pickup...although that could be me touching it with bare fingers, right?

Any ideas? I might lift the pickup out for inspection...not that I know what I'm looking for.

ICBM

That sounds like you have a short in one coil. Inspecting it probably won't tell you much - if it's a nearly complete short it will be where the inner end wire crosses the rest of the coil probably.

If it is that, the only fix is to rewind the coil.

Depending on how the coil split switching is arranged it might be a short to ground though, which could be in the pickup cable and will be fixable by replacing that.

Alegree

ICBM said:

That sounds like you have a short in one coil. Inspecting it probably won't tell you much - if it's a nearly complete short it will be where the inner end wire crosses the rest of the coil probably.

If it is that, the only fix is to rewind the coil.

Depending on how the coil split switching is arranged it might be a short to ground though, which could be in the pickup cable and will be fixable by replacing that.

There's tons of ways a pickup can short out, relatively few of them require rewinds, actually.

Most pickups that come to me 'requiring rewinds' require a little poking, prodding and insulating and that's all.

digitalkettle

Thanks both. It's a new guitar so there's a new pickup on the way.