When testing control board LEDs flash on then go off OR the old 1357 problem

Hi First time builder of shruthi -1 here, assembled filter board first and that went without any hitch … however when building the control board I am at the stage where I can power on and do a test before soldering the Screen.

At first I was getting the led 1,3,5,7 lighting up which after looking on here seems to be something to do with S6 - what readings should i be getting from the legs on S6? … Also I have checked the resistor network and all is ok there.

After getting nowhere I replaced the 165 shift register just in case I had fried it while powering up. Now when I power up either ALL the leds light up for a split second then go off totally OR I get the 1 3 5 7 problem ??

Is this fixable or have I killed something, will I end up having to get a new pcb and parts to build a fresh control board?


> what readings should i be getting from the legs on S6

IC2 pin 11 should be at +5V.

Hi thanks for the reply

I’m getting 4.95 on pin 11 of IC2 … is that ok or too low?

It’s ok.

Please post a photo of your control board (both sides)

Here goes, apologies for my horrific soldering - especially the reverse of pin2 on IC2

Do you think the board is ruined?

It’s not that bad, but some of these solder joints are a bit suspicious - especially those that look like “balls”. Try redoing all of them.


Ok having gone over and resoldered joints the leds now light up as desired YAY so thankyou very much for that :slight_smile:

So before moving any further I hooked the build up to my audio interface (tascam u600) and ran a single note midi pattern in ableton 9 … the audio signal from the shruthi is VERRRRRRY faint and when turning the encoders ie. cutoff there are many clicks and glitches … any ideas what may be causing this? The audio sockets seem to be soldered ok … on the plus side it appears that midi is working fine :slight_smile:


Post photos of your filter board, maybe we’ll be able to spot obvious mistakes.

Here is the filter board

If I turn the gain right up on my audio interface I can hear the shruthi (with a high amount of noise) but whenever I turn an encoder the sound is broken up and jittery even though I can hear the change in filter resonance and cutoff etc.

Thankyou for your patience

You have forgotten the bridges near the audio jacks (R1 and R2).

Don’t forget to turn down the gain on your audio interface!

DOH! Can’t believe I overlooked that …

Bridged those points and fired up … WOW I have to say it sounded amazing very pleased with that so went on to add the LCD screen. Lcd went on without a hitch and on powering up all the menus etc were fine… YAY

Happy with my success I mounted Shruthi in the metal enclosure and powered up

For the first couple of times she powered up ok and everything was visible but there was no sound …

Now I power up and the screen is blank and all LEDs light up …

Really hoping nothing has touched the metal case and fried

Please redo all solder joints…

Sometimes you think the board works - but it’s just luck - the lead of a component touching the PCB pad by accident rather than through a strong solder joint.

While redoing the joints … with IC2 on control board I have noticed that pin 2 appears to be very dull and/or has no pad (it could have come due to my mistake)… could this be the root of the problem (apart from my diabolical soldering) and if so how would I alleviate this?

If the pad has gone you’ll just get a blob of solder on the pin.

Your soldering doesn’t look too great in places. Not enough solder on some joints.

“If the pad has gone you’ll just get a blob of solder on the pin.”

That’s pretty much what is happening :frowning: along with black plastic from the board itself covering the area.

Is there anything I can do to fix this?

Find out where that pin is supposed to go and run a wire from it to that pad.

PCB Patching:


Thanks, I’ll give it a go tomorrow, I’ve had enough for today lol

If I can work out where to connect it of course