Good idea Jimmy with swapping the pickup connectors!  That should help narrow down the issue.

Rob, good luck!  Very interesting project.
Just for reference - I am aware of at least a couple of threads that have photos of other PF-5 circuits:
https://club.alembicguitars.net/index.php?topic=4619.msg55306#msg55306
https://club.alembicguitars.net/index.php?topic=8342.0 - Maybe take this with a grain of salt, as I'm not sure if this was completely "stock".

[links changed to current Club]

Really rooting for the restoration of #28!

Thanks, guys, and thanks for the photos as well, very clear examples

Good luck with the restoration! I hope it turns out to be something simple affecting the bridge pickup.

I switched the pickups and can confirm that both pickups work, which is great since I prefer the sound of these older pickups over the newer ones.  The other positive confirmation is that the electronics cavity is 1 3/8" deep, which is the same depth of my other 70s era Series basses.  So, a PF6 card mounted on the back of the brass plate will fit in this bass.  What is preventing the bridge pickup from making sound is still unknown.  Next step, follow up with the mothership. 

Thanks for the update.  That's great news that both pickups are alive.  That's going to be a sweet bass when you get it all dialed in.

Jimmy J

Rob, that's the best possible news. RW can easily suss out that circuit.

Great to see you bringing this one back to its full glory and excellent news that both pickups work. May not be as involved a restoration as originally thought.

Question for the group:

Should I have a local luthier lightly professionally sand and re-oil the finish to remove built up residue and smooth it out with a fresh oil finish, or leave it with its historic "mojo"?

Rob,  I'm not sure a professionally done cleaning would detract from the value.
After all,  it is #28.  It will always have the value of a very low number Alembic.

Thanks, Kenn, that's kind of what I was thinking too.

That would be a difficult choice if I was the owner.   There is beauty in either choice.

I vote for leaving the mojo, for the time being at least. I can imagine this being a good time to have it done, while you're having it restored so taking it apart and cleaning everything? I personally lean more toward "the dirt keeps the funk" school, but a lot of that is laziness on my part! (And I do wipe down and clean my instruments periodically) (And how much "mojo" is on there?)

The body is not bad, I was just thinking a nice smooth even finish would look nice and really make the nice grain pattern come through.  The neck has some build up on the back and I will probably clean that up and smooth it out a little.  Otherwise it is in very good shape. But we'll see, I might leave it as is as well. 

I wonder if this bass was a couple of years in the making...