Maestro FZ-1 Fuzztone Gut Shots

[BruceB]

Check out the gut shots on this auction that just ended.  All expected components except the input resistor (100K) and input cap (.01uF) are clearly visible. 

E*B*A*Y

1962 GIBSON MAESTRO FUZZ-TONE 1st ISSUE w/ PAF STICKER
EARLIEST PATENT APPLIED FOR MODEL FZ-1 #719 w/ 1962 AD

Item number: 160208698374

When I compare it to the schematics, I find some interesting (possible) differences.

As one of the "earliest" models, the 470K base-power supply on the second transistor is supposed to only be on FZ-1A. 

But that is a minor point compared to the white wire connecting the emitter of the second transistor to the third lug of the attack pot.  The emitter is almost certainly grounded by the sheet metal screw to chassis.  Which means the white wire would ground the third lug.  But, the base-100K and emitter of the third transistor are probably grounded to the Attack pot body (I can't really confirm this by the photos.)  If they aren't grounded to the body, the circuit doesn't make sense because having the Attack at maximum would ground out the signal.

Anyway I compare these photos to the schematic, it just doesn't look right.

[slacker]

Nice find, and nice first post

The wiring on that pot does look a bit odd. I'm not sure that the white wire goes to lug 3 though, to me it looks like it goes to the pot body. That would match the schematic assuming the resistor and Q3s emitter are also connected to the pot body.

[BruceB]

Thanks!

You're right, that's possible.  But, didn't all the fx of that era use the mechanical connection of the pot to the chassis to ground the body?

An example would be the way the Volume pot's third lug is bent back and soldered to the pot body.

[slacker]

You could be right the third lug could be connected to the pot body, I can't really tell from the photos. The resistor and emitter do look like they're soldered to the pot body though, so if the third lug was connected to the body as well then both ends of the pot would be grounded, which doesn't make much sense.
If they just wanted to ground the emitter and resistor it would have made more sense to connect the white wire to the same lug as the components, rather than relying on the connection through the pot body.

Hopefully someone else will have a better idea.

[BruceB]

Maybe not so mysterious after all...take a look at

Gibson FZ-1A Maestro Fuzz-Tone Guitar Pedal "Original"!        Item number: 200202034044

Only one shot of the circuit (second auction), but it is clear the white wire goes to the (almost certainly) "grounded to the back of the Attack pot" third lug.  The first lug is unattached. 

And if you look again at the first auction's shots, the first lug may have been pushed forward (toward the front of the box) and broken off, out of the way of the white wire.

I think where I went wrong was 'assuming' that the sheet metal screws were attached to tabs welded onto the sides of the box, thereby grounded.  If the circuit board were allowed to 'float', the sheet metal-looking screws having nuts to complete the attachment to the circuit board, the circuit would require wires to ground.  It's likely that the red battery wire is grounded by the foot switch or another wire underneath the board.