Minimoog D Pitch Bend modification (solved)

[Kevin Lightner]

I've been looking for hours on the net the schematics to insert the right value resistor, to no avail. Lots of people mention they have the mod, but nothing more.

I have the Moog modification outlined here. Shows a diagram of the resistor locations and values.
Hope that helps a bit.
Moog factory service bulletin 830 pitch wheel mod.

Seem to remember a similar mod published in Keyboard magazine years ago with the added opamp.

The resistors added on the old style board(s) is shown on the right correctly at 332K each. (3 total.)
But the resistor to be added on the newer style board(s) is shown in the right spot, but with no value note is provided.
It should be 619K.
(all should 1% metal film types.)

[thealien666]

...But the resistor to be added on the newer style board(s) is shown in the right spot, but with no value note is provided.
It should be 619K.
(all should 1% metal film types.)

I think the value is printed in bold lettering a little to the right (above two other components) ?

[chris j]

CZ rider, Kevin, Alain : Thanks a ton guys !!
I've been in touch with Rudi for the other mod aswell,I should be sorted now !

The mod I had was a mixture of both mods but uncorrectly wired...

[chris j]

You do know that the mechanical tension of the notch on the pitch bend wheel is adjustable, right ? Maybe yours is not tight enough ? When I got my Mini, I had to put just a tad more tension on it, because it had lost a bit of stiffness after some 36 years...

yes, actually when I bought it I'd loosened it because I thought it was too hard to get out of the detent, but I tightened it back since, still the slightest touch while in the detent changes the pitch by 30cents minimum !

[thealien666]

It's true that, even when tight, the slightest touch, up or down, results in +/- 10 cents on mine (actually measured).
But that's why I love it like that because it's easy to create some manual vibrato.
And if you think about it, it's not more sensitive than a guitar string when bending it for expressive purposes.

[chris j]

+/-10cents I probably could live with, but +/-30cents minimum (measured aswell), is too much. I like the effect you're mentionning, slight vibrato, but when I'm back from a real bend, I'm not back to zero, so instead of carrying on playing, I'm trying to set it back to the right position, with slight touches, until it's in tune. It's not right

[chris j]

By removing the resistor loop on the OSC 1 range selector, the deadband mod works now!
thanks everyone for your precious help !

[thealien666]

Woohoo !

[chris j]

woohoo indeed!
Resistor Loop assisted by his vicious sidekick -10V are the culprit in this riveting whodunnit set over a mock deadband mod background.
well done Mr Holmes !

[Kevin Lightner]

Let me see if I have this right. It's just a guess:

Owner has Mini with newer style osc board.
Mods it at one point for the zero detent mod.

But then, for whatever reason, sells or trades his newer board for an older one.
This leaves him with half a zero detent mod.
The half of the mod still left is on the mod section itself: the back to back diode, the 27K resistor and a -10 volt supply wire.
BUT... if he now has a newer style unmodded Osc board, he need needs to add a single 619K resistor as shown in the mod diagrams.
(Early osc boards get 3 332K resistors added, while later osc boards got a single 619K resistor added.)

So that's my guess: someone traded or bought or their osc board, but never undid... or redid... the zero detent mod that was appropriate for that particular osc board.

[chris j]

not quite

Owner has Mini with newer style osc board.

Owner has mini with old osc board

Mods it at one point for the zero detent mod.

yes but the mod from bulletin 830 (no OPAMP), brings in -10V to plug on pitch bend pot , puts the 27K on the OSC1 range selector, and the 3 resistors on the old board

But then, for whatever reason, sells or trades his newer board for an older one.

the opposite, trades the older one for a newer one, but more likely sells the whole machine and the new owner changes the board to a new one and doesn't know about the #830 mod.

This leaves him with half a zero detent mod.
The half of the mod still left is on the mod section itself: the back to back diode, the 27K resistor and a -10 volt supply wire.

I think the mod section was added at this point, (the 27K resistor is not on the mod section, it's on the OSC1 selector,
there are 3 resistors on the mod section, 100k 150k 200k) but for some reason the mod is wired in a strange fashion: ground going to the +input of the OPAMP, everything else going into the - input of the opamp, and the now unnecessary -10V going on the ground of the opamp and also on the pitch bend.

[chris j]

I've noticed that OSC2 is going +/- 5 semitones instead of 7, and OSC3 +/- only 4 semitones, don't think it was like that before, at least for OSC3. (note that I've had the mini for less than one month and it's my first analog synth)
Is there a way to set up the range of the oscillators ? I can live with them being like that though, but if there's a way I'll set them up at some point
cheers

[MC]

So that's my guess: someone traded or bought or their osc board, but never undid... or redid... the zero detent mod that was appropriate for that particular osc board.

Or they redid what was undid. Or they undid it to redid the undid that was redid. Or... Or... *HEAD EXPLODES*

[thealien666]

I've noticed that OSC2 is going +/- 5 semitones instead of 7, and OSC3 +/- only 4 semitones, don't think it was like that before, at least for OSC3.

Do you mean by using the pitch bend wheel ?

[chris j]

no I mean the osc frequency pots on the front pannel , marked -7 to +7 .
I also have the pitch bend going 3semitones down and 6 up (used to be 6 up and down)