2001 FNA - Strange Wiring Problem

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I have a FNA with a single humbucking pickup. I purchased the bass, new, in 2001.

The output on the bass recently died, and after checking the usual suspects, such as the output jack, I traced the problem back to the MEC pickup.

I pulled the MEC from the bass, and I could not get any reading off of it.

The bass came stock, from Warwick, with a Seymour Duncan STC-3M4 preamp. I could not locate a MEC pickup like the one on my bass, so I ordered a Seymour Duncan SMB-5A as a replacement. I read in a few places that Warwick had used those pickups at one time, and since the bass already had a Seymour preamp, I thought the two would be a good match.

I installed the pickup per the SMB-5A instructions, but I do not have any sound. If I pull the plug slightly out of the output jack, I can get some signal. It is almost as if the sound want to come through on the ground side of the plug.

I have connected the pickup straight to the jack, and it produces sound without any problem in that scenario. I've also used a meter to make sure power from the battery is getting to the preamp board and that continuity is good between all connection points.

I'm hoping someone has installed a Seymour SMB-5A in an FNA and can offer some insight, such as perhaps I need to deviate from the stock wiring diagram in some way.

If anyone can help, I would really appreciate it. I guess I can always gut the electronics and replace everything, but that seems like a drastic step.
 
to me kt sounds if ig wasnt the pu at all but rather the pre
 
Would the FNA make any sound with the trimpots turned all the way down?
 
The original pickup, when connected straight to the jack, produces no sound, but the new Seymour does (when connected direct). That leads me to believe its something with the preamp (trim pots are turned up), but it and the other components and connections appear to check out when tested in isolation.

I have been hoping that I would stumble across a "when you put an SMB-5A in a FNA you need to do this instead..." type of wiring, but I believe I the best course of action may be to gut the electronics and replace the preamps, pots, etc.
 
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