Where have I gone wrong? (Converting guitar from active to passive)

Dave_Mc

Hi everyone,

I decided to replace the EMGs in my Jackson with some Alegree passive pickups. I've got it all wired up, but when I test it with a multimeter (on a cable plugged into the jack socket), I'm getting readings which are quite a bit too low- 2.9k on the neck pickup (should be 7.4k) and 3.3k on the bridge pickup (should be 10.3k). The middle position is similarly too low (2.3k). The readings are almost around where I would expect parallel wiring to be?

I changed the pots to 500k log alphas. I kept the stock 3-way blade switch (and wired the Alegrees to the switch the same way the EMGs had been wired) and kept the stereo jack socket- I just snipped the wire which went from the battery to the jack socket. I *think* there was a ground wire coming from the bridge (there was a hole going in the general direction of the bridge, I'm not sure where else it was going to, and it was separate from the pickups' wiring cavities) and there were two ground wires coming from the shielding paint in the pickup cavities, which I just wired to ground. Oh and I checked the Alegrees on a multimeter before I installed them, and after I had them in the guitar but not wired up, and they're both fine.

Any ideas what I could have done wrong? I did some basic troubleshooting and some looking on the internet, but couldn't find anything. It's probably something simple and really dopey and presumably connected to changing from active to passive (which I haven't done before).

Thanks very much for any help you can give me,

Dave

Funkfingers

As ever, photographs of your wiring would speak volumes.

EMG wiring instructions for active pickups assert that a bridge ground connection is unnecessary. 

Seymour Duncan wiring instructions for their active Blackouts and Livewire pickups assert that a bridge ground is essential.

[Shrugs.]

Dave_Mc said:

The readings are almost around where I would expect parallel wiring to be?

This could well be the explanation. (I am being cagey about exactly what is connected in parallel with what else.)

Do you have any coil split, phase reversal or series/parallel mode switches in circuit?

If the humbuckers have 4-conductor + shield output cable, which pickup manufacturer's schematic wiring diagram did you follow?



EDIT: I deduce that you are using Alegree Indian Summer humbuckers. The online product description emphasises that bridge/Treble position unit has intentionally unbalanced coils whilst making no such comment about the neck/Rhythm pickup. Presumably, the latter has near as dammit balanced coils.

Inadvertently connecting either coil of the neck humbucker in parallel with the higher output coil of the bridge humbucker would yield c. 3.3k. Interconnecting the other two coils in parallel would yield c. 2.9k.

For me, the puzzling aspect is, how the hell have you achieved this? 

Dave_Mc

^ Thanks for your help

I'm not really sure how to post photos on here any more since Photobucket went weird  

I'm using a high output Bentbucker in the bridge and an Indian Summer in the neck. Like you, I thought unbalanced coils might explain it, but I was a bit sceptical it would be as big of a difference as that, especially since it's not mentioned on the Alegree site.

I don't have any fancy wiring at all, just regular humbucking on a 3-way switch. I'm using the Alegree colour-coded wiring (black is hot, red and bare are ground, white and green are wired together and taped off). I can't go back in time to be sure, but when I took the readings earlier before I'd wired them in I'm almost sure I used the same colour coding- and got the correct readings.

Regarding your last sentence- that's what's annoying me, too! I can usually trouble-shoot pretty easily (I've got quite good at it as I make so many mistakes! ), but this active to passive thing is what's throwing me. It could be that that's a red herring and I've done something else silly.

How would you wire the coils in parallel by accident? I guess you just use the wrong colour coding...

I'm wondering... could something be shorting out somewhere? On my Patrick Eggle New York, if you screwed the bridge humbucker surround in fully, it shorted out one of the coils somehow. Unscrewing the screw just slightly fixed it. I'm wondering if something similar is going on here...

ICBM

A contact between one of the pot terminals and the shielding paint is a possibility. What happens to the readings if you undo the pots and lift them clear of the cavity floor?

Dave_Mc

^ Thanks, that could well be it! It came with mini-pots and there are sort of cut-outs for them in the cavity- something could well be touching. I'll try that and report back. 

ICBM

If that is the cause, a piece of paper masking tape between the pot and the paint will fix it.

Dave_Mc

That's amazing, John, you're bang on (as usual)! It's the tone pot. Any ideas how to stop that shorting out? A wee bit of insulation tape under the terminals?

I'm just thinking I probably do have a few 500k mini pots lying around that I took out of my BC Rich (if I can remember where I put them!) so if that's a better way to fix it, I could just do that... I'm guessing the bigger ones are slightly better quality, though. EDIT: LOL, ninjaed I'll give that a go, thanks again for all your help  

ICBM

No genius required, just an encyclopedic memory for all the mistakes I’ve made in the past .

Interestingly, this also shows why paint is slightly less effective as a shield than foil. A short to foil would produce silence.

Funkfingers

ICBM said:

No genius required, just an encyclopedic memory for all the mistakes I’ve made in the past .

… or other people's bodge-ups that you have been expected to repair.

Dave_Mc

ICBM said:

No genius required, just an encyclopedic memory for all the mistakes I’ve made in the past .

Interestingly, this also shows why paint is slightly less effective as a shield than foil. A short to foil would produce silence.

That's usually how I troubleshoot too- remembering past mistakes! I don't think I'd have thought of it myself, but as soon as you said it, it jogged my memory that the new bigger pots were a bit of a tight fit. Actually I have a vague feeling that at the time I thought "I hope this doesn't come back to bite me!", but then promptly forgot... 

Actually I think another way to sort it (though more bother as it would require a bit of rewiring to lengthen some leads) would be to turn the tone pot round- for some reason there was more space in the cutout at the back of the tone pot. The volume pot had that extra space where the terminals were.

I didn't actually hear the pickups at the reduced resistance setting, I didn't have any strings on it at that point, but I trust my multimeter!  

Thanks again for saving me a ton of work... my next step would have been to rip out all the wiring and start again from scratch. Maybe with a new switch and jack socket as well! And I still might not have figured out what the problem was...

The pickups sound great, if anyone is interested. I think they're out of phase in the middle position, I must have put the Bentbucker in backwards (there's nothing to tell you which way round it should go). I'll swap the wires round tomorrow.