[Wannabe]

O.K.  something is wrong with my head.  I dabble in making my own guitars.  I have about 30 now, so I am not a novice.  I always use Dimarzio pickups.  The second to last guitar I built I put a super distortion in the bridge, hard mounted to the body.  It had a scream higher than a feedback that I could not get rid of.  Tried everything.  Bought a brand new superdistortion thinking it was the pickup and the same thing.  I chopped the guitar up and threw it away because after wiring it over a dozen times to the same fate, I knew it was something desperately wrong. 
Fast forward.  Just finished a new one and went with a crunch lab in the bridge.  The pickup has the same scream.  Seven different amps and 23 different wiring differences.  I bought a used crunch lab and it does the same thing.  I am ready to lose my mind in quite a serious way.  I put a washburn pickup in and no problem.  An ESP pickup and no problem.  Jackson, no problem.  The problem is they sound like crap.  What am I doing wrong??  3 way with single volume.  No spit coil, no nothing.  Running straight humbucker.  The neck pickups do not do this on either guitar.  The bridge only.  Is this something that anyone can understand or seen?  I went through all of the stickys and found nothing.
Any help may just save my life.

[darkbluemurder]

This is very difficult without seeing the actual guitar and wiring. I have never encountered this but I have seen other strange things but one thing is clear - if anything appears to be wrong there is usually a sound reason for it - the difficulty is finding it.

First thing I thought of was that hot and ground of the output jack were accidentally swapped - but then the neck pickup would have the same issue.

For the same reason we can rule out the switch and the volume control. And since other pickups did not show it in the same guitar I am inclined to rule out the guitar cable, amp and other equipment as well.

Have you checked if the Crunch Labs work in a different guitar? If not, the pickups may be faulty even though it is very unlikely that two pickups exhibit the same problem.

Good luck,
Stephan

[tonejam]

wire the PUP directly to a jack plug and plug it in. If problem, its a bad PUP. If no problem, it's your wiring, switch or pots.
Check it out one component at a time.

[Wannabe]

I did wire it directly to the output twice.  Well, one of the pickups twice and one once.  Still made that same high pitched scream.  Just can't get rid of it.  Sounds heavenly when hitting a chord, but as the chord dies down in volume, the scream takes over. 
I just can't figure out the connection.  Two guitars in a row and four pickups in a row.  (three brand new and one used)  I have to be doing something wrong.  Copper shielding too much, or the paint I use or something.  This is getting really frustrating.  Five weeks of construction, sanding, frets, 86 coats of paint.  Uhhhg.  I just want to play one show with the stupid thing before I throw it away.
Thanks for the help.
I may have to pull out the Fluke from work, take it home and test every parameter of the pickups I have not thrown away.

[darkbluemurder]

It is highly unlikely that the shielding is a problem - otherwise the neck pickup or the other bridge pickups you tried in that guitar would have the same issue. And if any hot part of the wire touched the shield you would not get a signal at all because it is shunt to ground.

I would test the questionable pickup(s) in a different guitar to see whether they act up there, too.

Was only the bridge pickup hard mounted or both pickups?

Does the scream only appear with distorted amp settings or with clean(er) settings as well?

Good luck,
Stephan

[Wannabe]

It screams in all settings.  Clean, distorted, and heavy gain.  I have taken the pickups out of the guitar and tried plugging them into the amp with no guitar around them and they sound fine.  Something about this guitar is making them do that.  I routed the pickup position about 2 mm further away from the Floyd than standard.  But I don't know how that could be any different. 
And yes, I did mount the neck pickup straight to the body exactly the same way as the bridge. 
This one has me stumped.

[darkbluemurder]

It screams in all settings.  Clean, distorted, and heavy gain. 

I think we can rule amp and other equipment out - a clean amp setting should not make anything scream.

I have taken the pickups out of the guitar and tried plugging them into the amp with no guitar around them and they sound fine. 

Sounds like the pickups for themselves are fine.

Something about this guitar is making them do that.  I routed the pickup position about 2 mm further away from the Floyd than standard.  But I don't know how that could be any different. 

This should not make any difference in the noise.

And yes, I did mount the neck pickup straight to the body exactly the same way as the bridge. 

Then we can also rule out the mounting method.

The only thing I can think of the moment is that there is some capacitive coupling between the pickup and maybe the copper shielding or shielding paint (if you used these) but then I wonder why it does not do it on the neck pickup. This is really puzzling.

I would rip out any copper shielding anyway. IMHO it's not necessary with humbuckers.

Cheers Stephan

[jazzfromhell]

Could it be......Satan? 

Sorry to hear about your problem, its indeed very puzzling.

[JohnnyGtar]

I once wired up a Strat with new PUPs (2 Bill Lawrence and a Duncan - all hum canceling pickups) for a buddy and ran into the same problem. All pickups fed back at ridiculously low volumes, even on a clean amp setting! To this day I don't know why I suspected that the pickguard (made of metal) was the culprit, but it turns out I was right. We slapped a plastic pickguard in and problem solved. I hope this helps.

[JohnnyGtar]

Have you tried the guitar in question in someone else's rig?

[darkbluemurder]

I once wired up a Strat with new PUPs (2 Bill Lawrence and a Duncan - all hum canceling pickups) for a buddy and ran into the same problem. All pickups fed back at ridiculously low volumes, even on a clean amp setting! To this day I don't know why I suspected that the pickguard (made of metal) was the culprit, but it turns out I was right. We slapped a plastic pickguard in and problem solved. I hope this helps.

Had a similar problem with two Bill Lawrence humcancelling tele pickups but they squealed only under gain. The culprit was the traditional steel tele bridge. Changing to a stainless steel bridge cured the squealing but I did not like the change in the tone.

Cheers Stephan

[Wannabe]

I sent the guitar off to Gutierrez guitars, as he thought I had done something wrong.  He played with it for days to the same fate.  There is something that neither of us can figure out.  He ended up putting an alnico8 Seymour Duncan in it.  It sounds decent and makes zero squeal. 
I don't give up very often, but I just had to on this one.  I think Jazz got it right.  So, I have 29 guitars now, and 28 1/2 have dimarzio pickups.  I am so vain that I may have to take some cleaning agent and take the Duncan letters off.  The guitar is too pretty for those.
Thanks for the help, gentlemen.  I really do appreciate the time and expertise.