Shruthi SMR4 mkII No Audio Out

I have been around for several days problem , with my new shruthi.
The display works. Midi apparently. As a note on the display. Problem now is : I have no signal in the audio out. either the test note , nor midi.
But when I had the assembled shurti it worked. It lay around for a while now and I wanted to test properly.

Measuring instrument is available.

Does anyone have an idea what signal path should I investigate ?

Sorry for my ugly english :wink:


At the bottom of the build page there is a chapter troubleshooting. You can check the signal at several places in this image.

Yes, I 've also seen. but how exactly am I supposed to measure and what I expect for values ​​? Should I as measured with a multimeter or cut a pawl cable and GND to GND and then points to the latest ?

You can use an audio cable. You connect the plug to a mixer or amp. You cut it and connect the shield to ground on the pcb. With the other open wire you check the points on the pcb.
You don’t have to use a multimeter. You are really listening to the signal at certain parts of the circuit.

ok I have now done. At points 1 and 2 I have a ton. At point 3 , on the TL074 , is no more.

Please post a photo of your board… Maybe a wrong resistor value somewhere or a transistor soldered backwards!

Looks all ok. How is the backside of your board? maybe you have a bad solder joint somewhere?

Voltage on IC4 pin 7 when cutoff = 0 and cutoff = 127?

yes, I also think that it will be. So again I have to go off all plumb. what I find funny is that in the beginning it really ever worked. I heard for example the snare preset.


I go eat. Then I check that @pichenettes

cutoff = 0 (2,3V)

cutoff = 127 (0V)

Check the soldering of the trimmer and of each pin of IC4.

Hi , sorry, I’m only now come to make the soldering to start fresh. But nothing changes. Everything like before. At point 3, I can still nothing hear.


I am now trying to understand the circuit diagram. IC2 between pin 1 and pin 3 of IC6 must be a connection. This I can not be measured by the continuity tester.


Where exactly on the board, the resistance (R36 10k)?

The continuity tester will not beep because IC2 pin 1 and IC6 pin 3 are connected through a 10k resistor. The continuity tester beeps when there’s a connection with little resistance (= short) between the points. This is not the case here. Check the soldering of all parts around IC4.

Hallo Haenger

If you have no scope, you can test the audiosignals with the Programm “Soundcard Scope”. ( or (

You solder a 2wire cable (GND and Signal) for your PC-Soundcard (Line-In) and make a contact with testpoints and GND.

J4 Pin1 : Osc-Signal
IC2 Pin1 : Mix
IC6 Pin7 : LP1
IC10 Pin1: LP2

good luck

Hello, I 'm sorry because of easter only now gotten to check the board. And I have desoldered the base of the IC4 times ( it was a work ) I’ve suspected as something was wrong. Besides I have a few points to the newly soldered IC4 Following stand I hear something very softly at the output Is quieter than the signal at point 1. But I hear what the output Does anyone have a tip for me ?

Hallo Haenger

Signals to IC4 are control signals but not a audio-signal. Follow the osc signal and test sound signal to IC2A Pin1 (Mix). Can you hear something ?