Tuesday, November 2, 2010

What I believe is a 1965 Supro Martinique, with a pickup problem

Back together ready for strings
This is a very unique pickups system built right into the bridge and bridge base of the guitar.  Looking at the bottom of the bridge base you can see 2 small squares with a small hole in the center.  These are 2 coils wound with the same thin pickup wire you would see on a strat or humbucking pickup, just a little smaller.
The 2 coils are connected in series with each other, wax holds it all in place and a single conductor shielded wire comes out to be connected to the controls.  Coming out from the bottom of the bridge top are 2 magnetic rods that when assembled to the bridge base slip freely through the 2 holes in the coils.  When the bridge vibrates, the magnets vibrate and breaks the field that the coils make and out comes the sound.
        One of the coils were broken, we had to melt the wax that held it all in place, rebuild and rewind the coil and get it all back in there.
There was also an intermittent short on the bridge side magnetic pickup.  I took off the cover and saw a loose coil wrap hanging our over the coil.  When you press down on the cover it shorted out.  Lucky enough it did not break.  I carefully tapped and waxed it to protect the wire and solidered the cover back on.  Worked great!
The 3 pairs of controls are unique, the neck pickups has a standard volume and tone control, the pickup near the bridge has a volume control and a bass cut for a tone control.  As you turn down that tone control the sound gets thinner.  This is what you see on many G & L guitars with passive tone circuitry, one treble cut and one bass cut.  The pickup that is built into the bridge has a standard volume and tone.  This pickup sounds best and is very usable with some of the tone rolled off.  The down side is there is no pickup blending.  At this point we just wanted to get the guitar to works as it would of stock.  Next time in I would recommend adding a way to blend combinations of the pickups, converting the magnetic pickup near the bridge to a standard vol and tone control and changing the values of the bridge pickup controls to give a little less attenuation.  There is a series wiring trick that I bet would work very well with this guitar.  That will be for next time.  Very glad to get it up and running in its stock configuration.

Empty Bobbin with the old coil wire removed

Funny movie on making a circle
Lining up the back of the coil form
Winding, slow and careful not to pull apart the coil
Ready to go back in
Those are the bottom of the 2 coils held in with wax
The 2 holes in the bridge line up with the center of the coils
The 2 pins coming out of the bottom of the bridge top are actually magnets


Loren said...

Now THAT is some impressive guitar repair. I love this blog; you guys are always taking me to school!

Christopher Ford said...

I have played out with it 3 times and the secret pickup you took so much time with sounds like sunshine raining down!!! Thanks Gary!