[SOLVED] No Sound from any testing point

Hi Guys,

I assembled the shruthi-1 mkII and I do not seem to have any output sound from any of the testing locations.

I have tested voltages since final construction and they all seem to be correct, the only semblance of sound I have achieved is a low level bleed at high gain on a mixer.

Please find attached pics.

Any help would be greatly appreciated.

Did you test sound on the OSC point on the control board side? Does the midi work? You should see a small ‘note’ sign in the left of the display.
You should cut of al the excess leads on the solder side of the boards. This might cause a short somewhere.

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there’s a lot of long component leads going on on the filter board. does the lcd work (you need to keep them as short as possible below the lcd)
maybe if you clean up a bit and resolder joints after cutting off long leads that can make shorts there’s already some progress

did you test the switches and leds before soldering the screen?

yeah, midi works.

yes, lcd works, scrolls through everything and it seems to work.

switches and leds all work fine.

ill clean up and report back tomorrow.

Sorry it has taken so long to reply, I’ve been busy with work.

Update, now I get signal at testing point 1, decreased level at 2, even lower at 3 and inaudable from then on.

At point 9 I can hear what I can only describe as a DC pulse.

I have tried resoldering everything and swapping the IC’s around with no change.

2nd update,

After racking my brain and trying to follow the signal flow and circuit diagram, I retested all the resistors on the filter board. Turns out the 7 of the 8 10ks near the poles are reading ~5k along with another 10k near test point 8. I’ll replace these tomorrow and report back.

Don’t replace them!.. You can’t measure a resistor in circuit… You are not only measuring the the resistor but also other parts of the circuitry that connect up ‘the other way around’… So often you’ ll get a different value. If you checked the colors it will be okay.

well all the colours are correct.

only thing I can see that is different is different ‘optional’ cap in the power section and i’m using a 12v supply.

Any tips on what to check next would be greatly appreciated.

Have you done the voltage test? Your 12V supply might be a 16V or 17V under light load and have destroyed the LT1054 :frowning: This would explain why the analog section (which no longer receives power) is entirely silent.

My first lesson in electronics: Always measure your AC adapter’s voltage. My clearly labelled 9v adapter was putting out ~13.5. A 12 volt may very well put out much more, as Olivier said :frowning:

what voltage should i be measuring?

the supply gives a reading of ~12.4 from the wall. retested the 5v from step 5 in the filter construction, everything comes up ~5 or -5.

Should I just order some more IC’s or is there a way to check they are broken?

Ordered new tl072, lm13700n and tl074.

No change in results.

What should I try next?

Do you have sound on the OSC> pin when a MIDI note is sent?


I have sound at point 1 and point 2 (albiet quieter). Point 3 quieter again and basically inaudible from that point on. Ill record the output and upload it.

File isn’t working. Basically, at half way on my amp, the main osc pin is loud, 2 is reasonably loud and 3 is really quiet. Then cranking the amp all the way up, pin 3 is reasonably loud, 4 is quiet and 5,6, 7 are inaudible. 8,9 both have the same output which is a low level ‘click’


is amp at full and on test point 9. The midi is being sent by an arduino cycling through midi notes.

Has anyone got any thoughts on this?

I keep touching problem areas up but nothing seems to be working.

What is the voltage at IC4 pin 7 with cutoff at 0 and cutoff at 127?

V @ cutoff 0 = 0.56V
v @ cutoff 127 = 0.56V