[sdiy] erratic Moog schematics (was: Tone control questions)

Michael Zacherl sdiy-mz01 at blauwurf.info
Tue Mar 11 12:28:31 CET 2014

Just yesterday I stumbled upon a missing connection on the 904c Filter Coupler schematic and some 2N3702s drawn as NPN on the keyboard circuits. That's on my paper copies I obtained some 25 years ago.
Since the footer says "Moog Music Inc." that docs should be from before 1975 under Norlin, one would think.
Anyway, so far on the Net I couldn't find other copies than the ones I already have. 
I found two or three corrected sheets but they are based on the aforementioned schematics.
Any hints were to get some more original, and more importantly correct, material?
Thanks, Michael.

On 11.Mar 2014, at 8:58 , Terry <daytona at verizon.net> wrote:

> Quite a few mistakes in those Norlin issued Moog modular schematics. These seem to be just simple copy mistakes where whoever copied these over from the original blueprints, did not proofread very well. Bottom line, if you are using the Norlin schematics, you are going to find these silly mistakes like 4.7K when they should have copied over 47K. Best to use the originals or a combination of the two copies.
> The Norlin issue 984 schematic has a few differences from 1967 the blueprint. You noticed the one pot labled 2.5K when they are all 25K pots. There is the bass circuit where the 4.7K is mislabled as 47K. The 80uF cap on the -6 rail is missing the +/- signs. And perhaps where you may be having a problem, the first resistor after the 22K mixer resistors is mislabled as 4.7K where it is 47K on the original blueprint. Could try subbing in 47K for that one?
> Another observation, the old circa 66/67 Moog circuits mostly used 2N2926 for NPN's and 2N3702 for PNP's. These were found in the early 901's oscillators, 902 VCA, 904 filters. By 1969 Moog was using 2N3392 for the same NPN's, and 2N4058 for the PNP's. Most schematics were updated with these, but that 984 schematic is the same revison from 1967. Wouldn't surprise me if those later 984's used the 2N3392's for the NPN's in that circuit. Guess you figured out those odd value filter caps are those Mallory tropical fish type. Would like to see a close up of an original board layout. The 984 had two circuit cards, each with two identical mixer circuits.


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