[sdiy] Blast from the past EFM VCO4d

crystal crystals at sonic.net
Sat Oct 18 01:22:17 CEST 2014

On 10/17/2014 3:03 PM, Tim Ressel wrote:
> If you don't mind a bit of *ahem* diy, the THAT300 (mouser) will work. It does waste 2 trannies, but the so does the 3046.
> Tim Ressel

DIY you say? why, no, i don't mind it one bit. i've been known to bend a 
few IC pins this way and that, attach jumpers, etc. i love it.

THAT300 looks good, it's a bit spendy but i suppose you get what you pay 


> 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
> http://www.linearsystems.com/assets/media/file/datasheets/LS310-3.pdf
> a good choice? if not what is these days?
> i recently purchased some of these smt matched pairs:
> http://www.nxp.com/products/bipolar_transistors/general_purpose_bipolar_transistors/matched_pair_transistors/BCM847BS.html
> but they are so small that even with a magnifier i doubt i can work with
> them.
> 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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