[sdiy] Blast from the past EFM VCO4d

crystal crystals at sonic.net
Fri Oct 17 19:55:07 CEST 2014

hi DIYers,

i recently discovered a pile of old EFM pcbs in my "well organized" room 
full of electronics junk. amongst them were some VCO4d (and 4e) boards. 
i'm thinking they would at very least make decent VCLFOs but perhaps 
with some work i could get serviceable VCOs with them. i'd like to get 8 
octaves of 1V/oct.

as per a harry bissell suggestion i am going to use a zener or precision 
reference zener in place of R32. i could swap out the LM3046 for a 
better matched pair (but i do have a bunch of them). is the LS312


a good choice? if not what is these days?
i recently purchased some of these smt matched pairs:


but they are so small that even with a magnifier i doubt i can work with 

does the FET  (J112) make any difference?

i know this has been hashed, rehashed, double extra super duper rehashed 
in years past. my ability to search the archives seems somewhat limited 
perhaps i am doing it wrong. any tips or pointer appreciated.

(a guy named) crystal



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