1979 Music Man Sabre I wiring questions

[Brooks78]

I'm looking for someone who has some experience with wiring a Leo Fender-era MM Sabre I or II guitar.
I bought a '79 Sabre I used, and I noticed that the tone pot does absolutely nothing. The pot appears to be functional after testing it with my DMM. The preamp appears to have been recently replaced with an aftermarket Griffin Effects PCB (I know that the originals were covered in goop to most likely prevent people from tracing it, an old guitar effect trick used in the infamous Klon, and every Pete Cornish pedal ).
Despite a pretty shoddy wiring job in the cavity, the continuity seems to check out everywhere, however, the Tone pot was replaced with a C500k pot rather than a C1M pot (as all existing documentation suggests it should have).
Despite all of this, the guitar is very underrated, and there are many usable tones when I manipulate the controls that are functional! i hope to solve the Tone pot mystery soon. Thanks for your help!

 

[beej]

Those original models predate the Ernie Ball era and there doesn't seem to be much discussion about them. Hopefully someone can provide a useful suggestion.

 

[Rod Trussbroken]

I'm looking for someone who has some experience with wiring a Leo Fender-era MM Sabre I or II guitar.
I bought a '79 Sabre I used, and I noticed that the tone pot does absolutely nothing. The pot appears to be functional after testing it with my DMM. The preamp appears to have been recently replaced with an aftermarket Griffin Effects PCB (I know that the originals were covered in goop to most likely prevent people from tracing it, an old guitar effect trick used in the infamous Klon, and every Pete Cornish pedal ).
Despite a pretty shoddy wiring job in the cavity, the continuity seems to check out everywhere, however, the Tone pot was replaced with a C500k pot rather than a C1M pot (as all existing documentation suggests it should have).
Despite all of this, the guitar is very underrated, and there are many usable tones when I manipulate the controls that are functional! i hope to solve the Tone pot mystery soon. Thanks for your help!

View attachment 49661

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I have the Pre-EB Sabre Guitar schematic. It has 3 pots:
Volume: 25K ohms
Treble: 1 Meg ohms
Bass: 100K ohms

How many controls do you have?

 

[Brooks78]

.
I have the Pre-EB Sabre Guitar schematic. It has 3 pots:
Volume: 25K ohms
Treble: 1 Meg ohms
Bass: 100K ohms

How many controls do you have?

I have all the same controls, and a Bright and a Bass switch. The only difference is the Treble pot is a 500k reverse taper pot (C500k) in my guitar, which I assume is a replacement for the original C1M pot.

 

[Rod Trussbroken]

I have all the same controls, and a Bright and a Bass switch. The only difference is the Treble pot is a 500k reverse taper pot (C500k) in my guitar, which I assume is a replacement for the original C1M pot.

.
I think your Treble control may be the problem. It should be a 1 Meg Log. I've double-checked the MM Pre-EB schematics for both the Pre-EB Sabre GUITAR and Pre-EB Sabre BASS.

Sabre GUITAR Treble: 1 Meg Ohm. Log taper.

Sabre BASS Treble: 1 Meg Ohm. Reverse Audio taper.

Perhaps ask "Griffin Effects" for a wiring schematic to trace the wiring and to check what pots they used.

 

[Brooks78]

Do you have a copy of the schematics? Everything that I've come across for the guitar has stated that the Tone pot was a C1M (1 meg reverse audio taper). The Griffin Effects installation notes call for a C1M, as well as the pages where you can build your own on vero board (see attached pictures).
What doesn't make sense is in the diagram below, they refer to the Tone pot as a "1M-L", and the other pots as 25k-A and 100k-A, as logarithmic and audio pots are the same thing.
I don't know my potentiometer labeling history, but I've always seen Audio/Log pots having the prefix "A" before their value, Linear pots having "B", and reverse taper having "C".

 

[Rod Trussbroken]

Hi.

I'd initially referred to the wiring schematic I have for the Sabre Guitar preamp. It has the same "L" for the Treble pot as in the first schematic you've posted above. I had interpreted the "L" to be a log taper update as opposed to the "Reverse Audio" taper used for the Treble pot in the StingRay Bass preamp (below).

I've looked at the preamp component diagrams for both the StingRay Bass and the Sabre Guitar (below). Both are pretty well the same and both show the Treble control to be "1M reverse log". Also, the StingRay Bass preamp wiring schematic shows "1M-RA" beneath the Treble control. No matter which way the Treble pot taper is named, it is the same for both the Sabre and StingRay preamps.

I have no idea what the "L" denotes.

If all is working ok with your preamp except the Treble (tone) then it must be the Treble pot itself or the wiring around it. Customer Service will have the 1 Meg Reverse Audio pot.

I have the Sabre Guitar hang-tag instruction manual that came with all new instruments. Let me know if you want a copy.

 

[Brooks78]

I would love a copy of the hang tag instruction manual!
I decided to try out two different guitar pots I had on hand (an A500k and an A250k) based on the advice of two different reputable guitar techs. The older tech told me to avoid reverse taper pots, as he thought they did little to nothing in any electronic application. The other tech doesn't even bother sourcing reverse log pots and just swaps the wires.
In any event, I tried both pots, even swapping the wires at poles 1 and 3 to check for an audible difference.
I settled on the A500k, as that pot had the most discernable sweep, (which was only at 1/16th of a turn) and the difference in tone was extremely subtle.
It seems to me like the Tone control pot in that guitar was an afterthought, and to get darker tones, the trick is to work with the Bass control and Phase switch.
As an aside, this guitar is clearly not a "plug-in and go" instrument that behaves like other electric guitars, but if you take your time to dial in your tone with all of the controls, it can sound really good!
I did manage to find a C1M pot on Reverb, but I'm not expecting that it will do much to the tone when it comes in the mail and I test it in the guitar.
l'll certainly report back if it does!