Blackout modular preamp: hum when using volume

[savat99]

Hi there, it's my first post on the forums! I have been visiting and finding useful information here over the years, but it's the first time I cannot find an answer and really need help.

I just had a Blackout Modular preamp installed by my guitar tech on my guitar (2 humbuckers 4 wires BHK pups that seem to have the same wiring pattern as SD's, and a 3-way switch). I really appreciate the upgrade but I have an issue. At full volume the sound is fine, no artefacts. But when lowering the volume on either pots, I get a loud humming/buzzing sound, even more so on the neck pup. I reviewed the installation, next to the official Seymour's diagrams, all seems normal. I even tried different wiring combinations on my pups (thanks to the solderless concept of this nice device), in the event my pickups were wrongfully installed, no luck.

I'm clueless. Ultimately, I can use my guitar as long as I remain at full volume (I'm not a fan of playing with volume on active pups), but I do use volume to mute my guitar, naturally.
Any hint as to why I get this loud hum would be gladly appreciated.

Cheers,
Luc

 

[Artie]

Re: Blackout modular preamp: hum when using volume

This sounds like a "ground" issue. I'd double-check to make sure the main control pot is grounded. There are several grounding pads on it to provide this. Don't count on the pickup wires themselves.
Just to be clear, the main pot, (with all the connectors on it), should be "solder" grounded.

And, welcome to the forum.

 

[savat99]

Re: Blackout modular preamp: hum when using volume

Thank you ArtieToo for the hint.
There are three ground connectors on the BMP; one already went to the input jack as per the design.
When I insert a wire in either one of the free ground connectors and ground it onto the bridge or any other metal components of the guitar, the sound simply goes dead silent. I mean, all sound, not just the hum.
Any more hint?

EDIT: I happened to have a spare 4 conductors humbucker. I swapped my current neck HB (since it's this volume pot which has the main issue) with my spare one and it yields the same result. I disconnected the neck HB from the Duncan Modular Preamp and same result (but no sound from neck pickup of course).
Further update: volume pot on bridge is fine, apart from a very feeble hum at around 9/10. I can live with this.
I checked and rechecked all wiring and soldering, which was accuratly done by my tech, all is conform.

So, bad neck volume pot?

UPDATE: problem solved! I tried a different pot, same issue. However, while removing the module, I saw a wire I hadn't seen before. It came from the bridge and was soldered as ground on the tone pot. I reviewed the design, it wasn't supposed to be there. I removed it from the pot and voilà! No more hum! I re-grounded it onto thew module by precaution, as suggested by ArtieToo.
I'm still experiencing a very minor issue though: the neck volume doesn't totally mute the guitar, the sound is still slightly audible; but I can live with it.