Redrawn Buchla 158A VCO schematic

[vladosh]

i never really cared about math , i like to explore as to what tip and tricks are there about a circuit ,and usually that's enough ..i only wish i could buy my parts from farnell or mouser or banzai or so ..i like to think they are more careful with fakes

[Fernando]

useless? it tells type, pinout and readings of any Si or Ge transistor or FET, plus resistance and capacitance both static and dynamic (photocell for instance), plus inductance, etc, etc. I'd say it's far from useless.

For FETs being out of reach for the ATMEGA tester you have that ultrasimple diagram from first link (you can use ATMEGA tester first to find out the pinout and consult datasheet)

[vladosh]

i dunno ,the one i got labels the P channel fet as PNP or NPN ,and the J112 like resistor so i don't really find it useful ,maybe that's useful for someone who understands more but it does not give me the pinout GDS ,can you show me what kind of tester you got ,or if you can suggest any ,it seems this that i got can read Mosfet but aparently not JFET
i got this one https://youtu.be/KS-JWDh0IbA

[Fernando]

I never used that newer tester model.

Mine is older, with the last firmware implemented, 1.13k
It's close to impossible to know the version in advance, they usually don't know it and wont look for it even if you explain how/whwre to look for it. So you have to risk. 1.12k is fine too

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[Fernando]

Why don't you open a thread for this? It will be interesting/helpful for many of us

[vladosh]

i just realized i have some PN4391 so i try it ,and it gives me just resistance of 20 or so ohms ,nevermind ..whole thing i thought the testers worked with jfets but i also see someone testing mosfets on yt also recognized as npn ,guess i'll just give it a shot about the 158 i planned to make 2 of those but if that doesn't work ..and it'll prolly be 2023 by then ,who knows what ..

[vladosh]

if anyone has more luck with JFETS ,here's my layout ,should be correct ,all npn pnp pairs used in the oscillator are matched BCM847/857

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[Fernando]

[vladosh]

i use the ones labeled as 123 ,nevermind really ,this is no big deal , i've built many 258's without this ,so it's all up to how correct is schematic , other thing i found at muffs is by la67 a comment ..the 1.5K resistors tied to the fet can be up to 2.5K if the transistor itself is off in idss ,someone has tried this and it works fine and it makes sense looking at the schematic ,i also found the same shaper in electronotes vco ,i am still waiting for the pcb's ..if it works great ,if not ..will have to find some other vco to replace it ,maybe pure sine vco from electronotes coupled with buchla timbre that also has a Jfet haha

[Fernando]

read ebolatone's blog (link up the thread), he used trimmers initially on that position

[Fernando]

[Fernando]

Just uploaded version 1.5 of my redrawn 158A schematic (just a few small graphic changes for more clarity)

BTW, it looks like a running dog!

[Fernando]

Re. "grey" unknown function wire:
Maybe it can be used as external freq. input while having "F" hardwired as "internal" for the freq. pot?
It looks like it

Anyone tried this or have new info about "grey"?