Why would a solid-body with 1 humbucker barely be heard through an amp?

[Rick Homan]

I set up a Fernandes solid-body with a passive humbucker for a friend and plugged it in to try it out. I wasn't sure it was even coming through the amp. I plugged my own guitar with a passive humbucker into the same amp with the same cable and it comes through loud & clear. The Fernandes is doing something because it's single pot and its coil-tap switch make minute differences. But there isn't enough output to shake a stick at. I took the cover off the rear compartment and everything seems still to be attached. I don't see a battery compartment anywhere.

Is there anything else I could check before handing this off to someone who really knows about wiring electrics?

[Jeffrey L. Suits]

Connect the pickup directly to the jack, see what you get.

[stevenrosburg]

You might have a short in the coils which would prevent it from having enough windings to produce effective output -- fewer windings is the methodology applied by active pickups, but they use an on-board preamp to boost the signal. As suggested, connect the pickup leads directly if possible. If it's a humbucker, you also probably have 4 leads if it has coil splitting, and you have to make sure you have the right leads.

[Tom Krebs]

An ohm meter would be valuable here testing the pickup and pots.

[Len Biglin]

A common fault is that when someone trims the wires before soldering , they accidentally hack into the insulation of the output wire and it shorts to the braid or earth wire . Or when soldering they overheat the wires and melt the insulation , allowing the signal to short to earth .Len

[FRANK]

i had a customer come to me with the same problem with a new guitar from GC it touck a drop so it was on sale anyways a magnet broke loss it still tested at 10,000K but only had half the sound output only seen one like it

[Rick Homan]

Thanks all! I got myself a multi-meter and poked around. It's a 5-wire humbucker, and both coils read 8k ohms, so I guess the p'up is okay. With the leads on the outer lugs of the pot, it reads from 16k ohms to 565k ohms as I turn the knob, so apparently it is functioning. So, there is just this single-pole switch to check out, or it is a wiring problem as has been suggested. I think I'll have to do some de-soldering to find the flaw.

BTW, I think my original report of extremely low output was just a case of wishful hearing. I am pretty sure now that in fact it has no output at all. Sure would be a lot easier if I looked in there and just found a loose end. I'll report back.

[FRANK]

WHAT BRAND HUMBUCKER DO YOU HAVE AND HOW MANY CONDUCTOR WIRE DO YOU HAVE SEYMOUR DUNCAN THE TWO RED AND WHITE TOGETHER BLACK TO PIN ONE ON THE VOLUME AND THE BRAIDED AND GREEN TOGETHER ON THE TOP OF THE POT FOR A GROUND DIMAZIO YOU CAN TIE'S BLACK AND WHITE TOGETHER RED GOES TO PIN ONE AND BRAIDED AND GREEN GO TO TOP OF THE POT FOR A GROUND AND IF YOU PU HAS A BRAIDED WIRE WITH THE WIRE INSIDE IT YOU CAN SOLIDER IT TO THE TOP FOR A GROUND AND THE HOT WIRE INSIDE TO PIN ONE IN PIN TWO FOR INDEPENDENT WIRING SO THE QUESTION IS WHAT KINDA PUI DO YOU HAVE ? WHAT KINDA POTS WHAT KINDA CAPACITOR SOMETIMES EVEN WHAT KINDA OUTPUT jACK

[Russell Vance]

Without wishing to draw the ire of all and sundry, if your level of understanding of the electrical side of the house is what it appears just take it to a electric guitar repairman as these 'simple things' can get ugly and expensive quickly.

Otherwize take out your soldering iron and connect the pickup directly to the jack to validate the pickup - make sure you know which wire is hot and which is ground and which is the 'series link/coil tap" if your reading 8k + 8k for both the coils and 16k total you're going to get something with a direct wire to the jack.

If you want to get serious, wire up a 'known good' jack with a couple of alligator clips and jump the pickup straight to the amp.

Once you have output, check each coil is good by gently tapping the magnets with a metal screwdriver and each will thump through the amp - better still use a tuning fork (steel/iron content needed here) which doesn't bump the magnets if your worried about that. If the pup is good, you are then looking at the pot, the selector switch or the coil tap switch (the coil tap switch the least likely as the pickup will work anyway even if the switch goes away open or short - at least half the pickup will output if the coil tap is wired conventionally). Hope this helps a bit, Rusty.

[Rick Homan]

No ire from me, Rusty, I assure you! My knowledge of this is rudimentary, but I have good teachers. Thanks for the practical suggestions, I will proceed with caution.

Thanks for asking, Paul! The pickup is a Seymour Duncan Invader, SH-8, in bridge position. Connections are as follows:

Black to center lug of pot, which my meter shows going to 500k ohms. One outer lug is bent to pot case and soldered; the other is empty.
Green and braided together to case of pot
Red and white together to center lug of single-pole switch. One end-lug of the switch is grounded to the case of the pot with an additional black wire. The other end-lug is empty.

Question: what is this switch doing? I had said coil tap because what else would a switch be doing on a guitar with one pickup; was I wrong?

How about using a jumper cable to connect the red&white with the additional black ground, thus closing that circuit and temporarily taking the switch out of the equation? If the guitar has output this way, would that tell me the switch is bad and replace it?

[Russell Vance]

Rick,
OK, the red and white wires joined together are the series link of the two pickup coils - it joins the two coils together in series to form a combination of the two coils which is cumulative in value (8k+8k for 16k total resistance of the unit) and humbucking because of the magnet/wind configuration of the two coils.
When the red and white wires are joined together by themselves it makes the unit complete as a humbucker.

When this red and white connection is earthed it effectively removes one of the coils by earthing out an 8k coil. So the circuit you have is a coil tap switch which halves the output and makes the pickup into a single coil, non-humbucking pickup (which will sound noisier due to it not being hum canceling but not as loud) when the switch is made to earth. Removing the switch from the circuit will not do much in this circumstance but you may remove the red and white wire connection and make sure the wire are soundly soldered together (if they are separated nothing will work).

Now, if the black wire is connected to the middle lug and one end of the pot has a lug soldered to earth you should have an output wire going to the jack (a 'hot' wire) from the other outside lug of the pot (which you say is presently vacant) and an earth wire from the jack going back to the pot body (earth). The red and white wires should go to the middle lug of the coil tap switch and the outer lug of the switch should be soldered via a wire to the pot body (earth). Tell me how this goes. Good luck, and if you are on the web go to Stewmac.com or Seymourduncan.com and navigate to their technical support areas and then to wiring schematics. Rusty

[Rick Homan]

Well, now, isn't that interesting! I think you have put your finger on it, Rusty. Presently, the black (hot) wire from the p'up goes to the middle lug of the pot, and the the insulated wire from the jack is soldered to that same center lug, leaving one outer lug empty and the other bent and soldered to the pot case. The sleeve from the jack's wire is properly grounded to the pot case.

I checked wiring diagrams at both sites you suggested, and they agree: it should be p'up's black (hot) wire to outer lug and jack's hot wire to center lug. So, apparently I should move the p'up's hot wire to the un-occupied outer lug. Note to self: in future start by consulting a wiring diagram!

I'll report back when I have had a chance to try this. Meanwhile, thanks Rusty and all for your help.

[Rick Homan]

Moving the pup hot to the outer lug did NOT do the trick, so I de-soldered everything, and wired the pup to the jack. The multi-meter showed 17k ohms all the way to contacts on the jack, so I figured I had it. I plugged it to the amp . . . Nothing! Fortunately, I had pulled the jack out of the body to make sure its wires were still connected, so I noticed a big brown blob on the jack's spring contact. A little scrape, a little steel wool, and we had lift off! Everything works, now! Thanks again everyone!