Crazy Shruti

well i got my shruti built (apart from the CEM chip which i left out for now…) and it powers up OK but it’s crazy. the LEDs are lit all the time, and the display flickers between parameters. none of the pots or buttons work. i checked the whole thing through for shorts on the ribbon cable etc, didn’t see a problem (i don’t usually have construction errors). at this point i’m thinking i might have a bad 595 or 4051. anyone else seen anything similar?



I’m ruling out the 595 or 4051 defect because if one of those chip died, you would either get messy LED patterns but stable display ; or messy pots/keys readings but stable LED output. Are you sure the ribbon cables are wired correctly? (I don’t mean wired backward, but maybe two leads could have been swapped).

The display flickers between parameters… but is it always on the filter page or does it seem to move from one page to the other?

Have you checked the continuity between each output/input, with the connector in place, from one PCB to the other.

Note that you can bypass the CEM3379 and still test the raw waveforms:

well i’ve checked the ribbon about 37 times now and i’m pretty sure it’s sorted. no swaps, no shorts, no crossovers, and good continuity between the ends of the cable. the LED does flicker every now and again but does sit on the filter page most of the time. the LEDs are all on, permanently. also checked the 595 and 4051 orientation. all are socketed. there’s not much to go wrong, i’m a little baffled to be honest. however i am going through a period of project problems… could be mercury retrograde?