Shruthi wont work

Im building the Shruthi-1 with SM4-filter.
When I’m connecting the two boards and power it up nothing happens.
I haven’t soldered the LCD on the controller board yet, but done with the filterboard.

I think the filterboard is good to go. I measured IC2 and IC6 and evereything was correct (+5V between the O pin and the middle pin of IC6,
and -5V between pin O and the pin on the right of IC2.)
But no LEDs lights up when I try to power up the controllerboard (with the filterboard).
What can be wrong?

Btw, my adapter has a light on it and it stays lit when powering just the filterboard. But when I connect the two boards, the light on the adapter slowly fades on and off. I don’t know what this means but maybe somone else does?

I’ve not soldered anything like this before, so help would be much appreciated! :slight_smile:


Is there a short between the +5V and GND pin on the digital board?

Thanks for your reply pichenettes.

So I measured between the +5v and GND point on the controllerboard, and first the numbers jumps up and down but stops on 1.7 (the multimeter is on 20k).
I don’t know what this means. Should this number be 0 ? Does that mean that there’s a short somewhere?

Btw, when Im measuering the same points on the filter board, it reads 7.8.

I checked the points on both boards in “continuity check”-mode with a multimeter, and it didn’t beep. This means there’s no shorts?

Well I have no idea why, but suddenly it just worked. Hehe. The 3rd and 7th LED lighted up, and all buttons worked.
Im gonne solder the LCD and test everything in a moment.

Arghhh… wait! Just go over all your solder joints - you won’t be able to do that once the LCD is on. It’s probably a cold joint somewhere…

pichenettes: I checked all the solder joints, and everything looked fine.
So now the LCD works, all the LEDs and buttons BUT, I only get sound when I have the jumper on 2 poles.
When I have it on 4 poles, I only get a “blop” sound.
I tried to resolder the three “jumper pins”, but nothing happens.
Where can the problem be? I’m so close now! Can’t wait to finish it!

If you have no resonance at all -> The signal chain is broken at the 3rd or 4th pole of the filter. Check everything around (above and below) IC8 and IC9.

If you have resonance -> it must be a problem with the 3 pin connector / jumper.

I have no resonance, so Im checking it right now! Thanks for super quick reply!

Found the problem! A bad solder joint.
Thank you very much pichenettes!