Am I nuts?

[tedmich]

(based solely on data below!)
I just tore down my amp because it started to sound like crap; thin, low sustain and thready break up at high gain settings. I though I had burned my PA tubes as I run it full on with an attenuator in the FX loop, but the JJ 6L6s were only 3mo old. Swapped out preamp tubes and looked for failing coupling cap but culprit was my guitar PU shield wire, which I inadvertently left off the ground connection while re-soldering my kill switch.

Its (1) Carvin M22SD with shield braid, Blk/neutral and Red/hot wires (Wht-Grn cause I don't coil tap). Reconnected the braid-Blk and my sound is back...

wouldn't have though this would ruin my PU, just made it noisier, gotta reexamine this part of my circuit!

[David Schwab]

The braid needs to be grounded, as does the black wire. Why would that make it noisier?

[g1]

What I think he meant was if the shield was not grounded, the pickup should function correctly but just be noisier.
Tedmich: are you saying the white is connected to the green? That would be single coil mode? Not sure what you mean by "neutral", is the black grounded?

pickup_wiring-rev2008.pdf

[tedmich]

Grn-Wht always connected as per the instructions you posted.

I had Blk going to Jack OUT/ring and Red going to Jack OUT/tip and left wire braid shield disconnected, but it sounded awful until wire braid shield was connected to Blk. I thought wire braid shield was just to guard against interference over the short wire run from control cavity to pickup body, but it appears to be more important than that.

[jonson]

What I think he meant was if the shield was not grounded, the pickup should function correctly but just be noisier.
Tedmich: are you saying the white is connected to the green? That would be single coil mode? Not sure what you mean by "neutral", is the black grounded?

[ATTACH]17313[/ATTACH]

Only single coil mode if grounded/ otherwise correct..

[Arthur Dent]

That braided shield isn't just for shielding, it is also the ground wire. If it's not connected, it would be like trying to power something with only one side of an AC outlet. Voltage is relative, and the ground is what the signal is supposed to be relative to.

[David King]

Was this pickup wired 3 wire and then rewired to 4 wire?

[tedmich]

no Dave, its a std Carvin 4 wire HB:
Red
White
Black
Green

with a braided shield

[g1]

Here's my understanding of the internal pickup connections:

The shield wire would be shielding the 4 conductors and connected to the baseplate which would not be connected to any of the coil wires.
I would think it should function as a coil without the shield.
I suppose a winding could be shorted to the baseplate combined with an open at the black.
Does it give normal resistance reading red to black, and open between shield and all 4 conductors?

[David Schwab]

Grn-Wht always connected as per the instructions you posted.

I had Blk going to Jack OUT/ring and Red going to Jack OUT/tip and left wire braid shield disconnected, but it sounded awful until wire braid shield was connected to Blk. I thought wire braid shield was just to guard against interference over the short wire run from control cavity to pickup body, but it appears to be more important than that.

The braid grounds all the metal parts on the pickup, not just the cable.

But the pickup should work fine without that connected. It really should be connected however.

[David King]

I've seen HBs with a start wire soldered to the base-plate along with the shield, this is always the case with 2-wire HBs. As g-one points out two things would have to be going on to get the results you got. Find out which if any of the 4 wires is connected to the baseplate and make sure that's also your ground color, i.e. black in the case of Carvin.

Why use the ring connection on the jack as your ground? It should work but that's often the first circuit to go bad on a jack. Tie it to the sleeve if you need more lug space for a star grounding schema.

[David Schwab]

Here's my understanding of the internal pickup connections:
[ATTACH=CONFIG]17325[/ATTACH]
The shield wire would be shielding the 4 conductors and connected to the baseplate which would not be connected to any of the coil wires.
I would think it should function as a coil without the shield.
I suppose a winding could be shorted to the baseplate combined with an open at the black.
Does it give normal resistance reading red to black, and open between shield and all 4 conductors?

I'd take a meter and check each wire against the shield. There may be a short or an open connection somewhere.

[tedmich]

I am tempted to wire in a toggle and record clips to show how bad it sounded, a bit mysterious but I am very happy it sounds better now!

[tedmich]

I'd take a meter and check each wire against the shield. There may be a short or an open connection somewhere.

will do David S. ! My current amp (hot rodded PV ULTRA+) is a complete monster but I think my PU is now the weakest link!