Model D problems: OSC 2 range: it control OSC 1 & 3

hello guys amd thanks again for the great community about moogs!
i’m the proud owner of a 1974 minimoog 6447 wich i’m restoring and now is in near perfect working order but remain an huge unique problem to fix:

The OSC 1 and OSC 3 works very good,
they tuned perfectly and make their work, but

if i move the RANGE SWITCH of the OSC 2 it affect the RANGE of the other two oscillators (the OSC 1 and the OSC 3).

This happen with or without the OSC 2 sqitch ON in the mixer section.

the only way to mantain the range of the OSC 1 and the OSC 3 right is to set the OSC 2 range to LO.
in this way the OSC 1 and the 3 works good but the OSC 2 in LO mode is unusable.


Musically speaking if i press A on the keyboard with the two working oscillators ON and i move the OSC 2 RANGE switch from LO i obtain:


OSC 2 in LO range = the other two oscillators at unison in 16’ range works good and maintain the A note.
OSC 2 in 32’ range = the other two oscillators at unison in 16’ range sound the F# note.
OSC 2 in 16’ range = the other two oscillators at unison in 16’ range sound the G# note.
OSC 2 in 8’ range = the other two oscillators at unison in 16’ range sound the E note.
OSC 2 in 4’ range = the other two oscillators at unison in 16’ range sound the C note.
OSC 2 in 2’ range = the other two oscillators at unison in 16’ range works good and maintain the A note as in LO range.



i hope i was as clear as possible
any help to solve this problem?

thanks to all
ciccio

Check that little buffer board for the octave switches

here it is a small video i’ve made to show the problem

http://www.youtube.com/watch?hl=it&v=PNBj7RowUnk

also i’ve see at the same RANGE settings the OSC 3 is an octave lower than OSC 1…

hi guys
today finally i’ve solved the problems! A special thanks go to Steve Jones from www.synthrepairs.com, as he said, was a faulty LM741 (IC2) on the octave buffer board, now the oscillators sings perfectly!

thanks again!



You’re welcome