[sdiy] Moog 904b high pass filter cloning... beware!!

[Jean-Pierre Desrochers]

Hi list,

For those who would consider working on a Moog 904B high pass filter 
clone
read this carefully..
Carsten Toensmann from www.analog-monster.de
has been working thoroughly on some Moog module clones
Like this one:

http://www.analog-monster.de/mmt904b_en.html

He kindly replied to many of my requests about
the good and bad surprises he encountered while
building its clone(s)..
And he submitted warnings about one 904B drawing
that was not working at all (spice model AND hardwired tests included).
He checked and modified some parts of the CV mixers that had errors
in the drawing version 6-23-70 like this one:

http://www.freeinfosociety.com/electronics/schemview.php?id=944

With its modifications he has been able to get the filter to work.
Please note that there were no errors in the original 1968 drawing:
(sorry.. bad scan but you can see both working CV mixers wiring..)

http://davealex.com/wp-content/flagallery/moog-blueprint-schematics/tn_moogschematics-904b_hpf-8749.jpg

So I put a 'revised' working version of this 6-23-70 drawing here:

http://www.arcenson.com/public/moog_904b_corrected_drawing.pdf

Enjoy !
J-Pierre