shruti-1 took a hard power hit that seems to have reached vca/vcf (cem 3379). Second oppinion pls. No cut res env response, sound still at audio amp out but no real adsr. goes from super dry to super sustain using rel. any spare 3379’s out there?
FYI replaced both + and - voltage regulators and charge pump seems to be ok as it was a reverse polarity 12 vdc (wrong charger) which caused all this mess.
There is a polarity protection diode in there so it shouldn’t cause damage to use a wrong polarity power adapter.
Did you measure your voltages? Do you have +5 and -5 V?
I didn’t see the diode, and I had to replace both lm7805 and 7905. I have power now, but no real vcf response. I think the charge pump is okay. Please consider this is the original shruti. I may reload the OS after patch dumps.
Oh orginal shruti ! … That’s before my time. I don’t know if there is a diode on that one.
No prob
Oliver still has the scheme on githhub. Thanks.
What I’m really wondering is why I get no change when tweaking the cut, res, env, lfo knobs.
There is no diode in this version, but I will likely add one.
The curtis chip uses both VEE (-5vdc) and VCC (+5vdc) But I have no VEE. Looks like a power failure after all.
IC5 is the charge pump and creates the negative voltage which is then regulated into VEE by IC1. I am looking for significant negative voltage at the output IC5 pin 5 and IC5 pin 3 which I do not have. I assume I will need to replace IC5 after all, so I’ve placed my parts order.
If you don’t have a -5V rail, the CEM3379 won’t work at all. It might be the MAX1044 as you suspect.
Thanks for the second opinion. You are right on the money, It was the charge pump. VCA/VCF is up and running again. And I still have all my patches!
