Hi all...Help on 921 tempco

System 55 • System 35 • Model 15
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xxwright
Posts: 1
Joined: Wed Jan 12, 2022 5:15 pm

Hi all...Help on 921 tempco

Post by xxwright » Thu Jan 13, 2022 5:34 pm

Hi,

which type of tempco is used for the 921 VCO, and how is it mounted?

dombedos
Posts: 16
Joined: Sat Mar 05, 2011 6:04 am

Re: Hi all...Help on 921 tempco

Post by dombedos » Wed Jan 26, 2022 6:54 pm

Hi,

the tempco used for the 921 are 1k±3% TC. In the original Moog construction they used Tel Labs Q81, which nowadays are quite hard to find. I purchased mines from Synth Cube some years ago; don't remember the exact part number.

According to the original Moog 921 construction, the TC is mounted under IC508 (3046), that is mounted on sil sockets, so that enough room is available for the TC. Here are some close-ups taken from my 921 clone.


IMG_20220115_184938.jpg

This is the same, with the IC removed, showing how the TC is mounted.
The TC should be in touch with the bottom side of the IC, with some heat sink compound, to improve thermal coupling

IMG_20220124_162642.jpg
IMG_20220124_162624.jpg

Hope this helps

All the best
Leonardo

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