The Last Bass Outpost

This sounds like the one I repaired for you, it was a bad connection to the coil under some 50 year old dead tape.  Very brittle, hard to repair under the microscope (I don't see very well anymore....).  It might have failed again, or it might be the connection on the *other* coil....sorry!

XLNT.....will give a try

Hardcore, shit, that weren't nothing.  While getting ready for our transnational outing, I was putting new pistons and cylinders (from JC Whitney--remember them?) on my bug.  They were "high compression".  I think 7.8:1.  Whew.  Stand Back!  Anyway, while putting them on, I didn't have the band clamp set right and broke one of the top rings.

No sweat, head down to the import parts store and get another set.  Back at the bug, find out that the top ring for my "hi compression" pistons was only 1.5mm thick vs the standards which were 2mm.  Crap.  Went to a couple of machine shops who just shook their heads.

I was not going to miss our convoy out of Gainesville to our Bright Future in Hollywood.  Filled with automotive mayhem--Marty's van ate an alternator in a rainstorm in Biloxi, Carl's Sprite a valve in Tucson, etc.

I had to remove .5mm off that ring.  Armed with a plate of glass off an old TV front (they were flat back then), some silicon carbide dust from my parent's rock tumbler, and an orbital sander, I proceeded to grind away that .5mm, checking for high spots with a micrometer, and pressing harder on those areas, until I had the ring ground down to 1.5mm all the way around.  Carefully put that sucker in and ran that baby all the way out to CA, and still running strong when I sold it several years later.

Baz, here is your pickup report...
An unusual pickup design—two coils, each serving two strings, like a P bass.  But each coil is on the opposite pole of a central magnet shared by both coils.  And each coil has an secondary magnet mounted to the outside of the coil, which energizes one of the two pole pieces that each coil has.  So, a total of three magnets, four pole pieces, and 2 coils.

The two coils should be wired out of phase to cancel induced mag field noise, and since they are on opposite poles of the magnet, the string signals will still be in phase, like in all humbuckers.

In pix1, we see the central magnet, where the yellow paint is indicating the N pole of the magnet.  The 2 pieces of copper foil are to ground the steel pole pieces, so they will not pick up noise.  The foil wrap touches the steel at the interface between the central magnet and the pole piece . One coil was where all the damage is, and the other is at the other side of the magnet where you see the 2 steel pole pieces.

In pix2 you can see the secondary magnet, its purpose is to magnetically energize the lower of the two pole pieces (it isn't touching the central magnet, so it isn't energized by it—hence the need for another magnet).  Why not a single steel pole piece?  I suspect it is an attempt to reduce eddy current losses in the pole piece, tho I doubt it is necessary, and a single pole piece would make the pickup much easier to build.

In coil1 you can see the 2 pole pieces, the secondary magnet, and the copper coil wires.

Specs:

Central magnet:  Ferrite, .2” X .55” X 2.35”  ~140mT pole strength
Secondary magnet: Ferrite, .2” X .2” X 1.2” (about half as long 'cause it only covers one coil) ~110mT pole strength.
Pole pieces: cold rolled steel,  .062” X .7” X 1.135”
Bobbin: molded plastic, .385” tall, .56” wide, length over all 1.5”.  Winding area .3” tall,.285” wide, 1.26” long.  Pole slot 1.13” long X .185” wide.
Coil: wound with AWG 44 solderable.  Intact coil measures  5.50Kohm, L 2.628H, Q 2.641 at 1kHz. (this is with the iron inside, raw coil would be lower L and Q).  I estimate between 4500 and 6500Turns. You'd have to wind one and sneak up on the final value.

Probably a pretty powerful and yet bright pickup.  The overall R would be about 10K (2 coils) and about 5.2H.  Not much losses due to the 2 pole pieces and the ferrite magnets (much less lossy than alnico)
Maybe not very warm sounding, ferrites tend not to sound that way.

Hi Baz, looks like I dropped the ball on that one, sorry, but you *do* have my email and phone number, you could have given me a kick in the butt to remind me.  I do have the pickup, is this the one?  If so, I'll get to it later this week.  OK to post at this forum?

Okay, I'm giving up on the pickup. Bought this 60's Hofner pickup off eBay:

http://www.ebay.com/itm/180935982978?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_500wt_716



Maybe later I'll try to fix the original pickup.

wow that looks just like the pickups on my japanese Pan bass.  I guess Hofner is where they cloned them from .  I'd be happy to fix that pickup for you, mainly just to see whats inside.  It might just be an internal solder joint.  Charge a nominal fee-not much, tho I might have to buy a reel of wire, if it turns out to be something I don't stock. email at thunderbucker@gmail.com

That CAD has a low end down to 25hz, that's not bad for that kind of money
Rick

Yeah, if you solo that channel you get a thumm-thumm  and not much more, that mic has a lot of low end and very little hi end, which is actually OK cuz you don't want a lot the other drum noise bleeding in there.  The impact of the kick turns up in the overheads and any mic used for the snare bottoms.