This can't work...can it?

[gramophoneshane]

This is a little off topic for acoustic phonos, but seeing there's a few of us here into the early electric stuff, I thought I'd post it.

I bought this some time ago, & a couple nights back I thought I'd replace the rubber components & get her up & running again.
Unfortunately I ran across something that I've never found before.

I removed the pick-up casing. Everything looked fairly normal so far.

Got the soldering iron out & detatched the wires from their mount & removed the mount.

Then I removed the magnet, and the plate that should normally cover the coil...except there is no coil in the regular sense. At first I thought someone had removed the coil & attempted to make their own by winding some wire directly to the needle bar, but the whole design of the mounts etc, dont leave near enough room for a regular coil. The wire around the needle bar also appears to be original.

So, has anyone ever come across this set-up before?
Normally the needle bar is insulated & suspended through the centre of a coil, and the movement of the needle bar within the coils magnetic field is what transfers to sound.
I'm not quite sure how this one would work- if it ever worked at all.
The needle bar is still insulated from the outer magnetic field, but the windings of wire around the needle bar don't seem to be enough in my mind, to create a decent magnetic field of it's own, and if it does, the pick-up can't be very sensitive.
Could it be an early (or failed) attempt at making a pick-up of extremely low output?
Is anyone familiar with this weird design?
I'd love to get it working again, so any info or advise will be greatly appreciated.

[Phototone]

Thats enough wire to make a good signal with that big horseshoe magnet. It's just a different way of doing it. Perhaps it is lower output, but maybe its just lower impedence.

[gregbogantz]

Your pickup appears to have been reworked by someone who didn't have access to the original type coil. It probably works. Just about ANY arrangement of a coil of wire in the general vicinity of a magnet and with a ferrous wiggling part will generate a signal.

This design actually makes sense. There is magnetic flux in the needle bar since it is positioned between the pole pieces of the magnet. The flux is minimal when both ends of the bar are positioned exactly between the poles. When the bar is wiggled one way, one end moves closer to the N pole and the other moves toward the S pole which causes the flux to increase in the bar in one direction. When the bar is wiggled the other direction, the flux reverses in the bar as its two ends change position. It's this CHANGING flux that creates an electrical potential in the coil which is wrapped around the needle bar. Whether this setup makes more or less voltage than the original coil will depend on the number of turns of wire in the coil and the strength of the magnet. It appears that there are fewer turns than in the stock arrangement, but the magnetic circuit may be more efficient than the stock arrangement, so you may have sufficient voltage anyway. Can't hurt to try it. Also, most of these old horseshoe magnets were made of low retentivity alloy and will benefit greatly from a re-magnetization to strengthen them and provide more output voltage.

[gramophoneshane]

Thank you gentlemen.
I'll replace the rubber & reassemble the pick-up tomorrow & hope for the best

[Swing Band Heaven]

Its a very interesting set up - double coils i've seen but never something like that. Will be interested to see what kind of output you get from it. Keep us posted.

S-B-H

[Skihawx]

I don't know if this will work. The coil has to cut the
magnetic lines of flux with movement from the needle. The
fixed coild works when the tail moves inside the coil with
flux lines picked up by the magnet. The coils look on
axis to the rotation or movement from the needle. Maybe someone
was playing.