No sound on first test [solved]

I’ve connected the two boards - not yet connected the display. All the switches, pots and LEDs are doing stuff - the correct LEDs light up on power up and pressing the knobs etc changes the patterns of the lit LEDs. I then connected the output to my amp and the midi in to my keyboard and… nothing except a few quiet pops and hisses. I pressed S1 to turn on the osc - it produced an audible hiss but no tone. also, I get popping sounds when I play the keyboard, but nothing else. I am reluctant to solder the display at this point, in case the source of the problem is under the display pcb. Any suggestions?

take an old(!) earplug or earphone and connect 2 clip leads, one to GND and the other one to OSC>.
That way try to trace down to signal to your audio output. Maybe the schematics help?

Thanks - I’ll give it a try

Please don’t put the earplugs or earphones in your ears. Static’s procedure is correct, but the sound level will be extremely high.

Using the same procedure you can try to find out at which stage the signal chain is broken:

All I’m getting is some crackle and hiss and a very low-level high pitched whistle - it could be the osc, but it’s very faint compared to the hiss

true that, sorry I should have mentioned

… ha?

use old(!) crappy speakers instead, if you got some lying around.

Hello Pichenettes. I didn’t put the earphone in my ear - I connected to an amp:) Only a very low level whistle at 1 9and lots of static!

somehow you have to make sure the program is starting up … correctly. I think you have to push S1 for a while, like 5-10s?

I suspect bad soldering. I built my first synth in the 1970s, so I know a bit of soldering, but my eyes are getting bad - I didn’t realise how bad until I started building this kit!

audio connected to ground?

Hi static - I did that - pushed S1 for a few seconds - when I released it I got hiss but no tone - I think the problem might be very early in the audio chain

Yes - one lead connected to Osc, the other to ground

I actually haven’t finished my full shruthi yet, only power and the control board. Try to think of a solution, it will always be obvious (or less obvious sometimes) in the end. You said the correct LEDs light up when powering up and switching work? Post a picture, …
yes you should be carefull with soldering. Take only the control board and connect the power supply (2wires) from the filter board to isolate the problem.
also, when not connected, of course, test your solder points with the multimeter.
first the cb, only than the fb

and go thru all the parts again, make sure you put everything in where it should be and with regards to polarity …

OK - thanks - I’ll go through all the things you’ve suggested

Posting high-res pictures of your board on this forum will be helpful. Holding the S1 switch for a long time is only necessary if you don’t have any MIDI input to test. Even without pressing S1, you should get some extremely loud signal on the OSC> pin whenever the unit receives a MIDI note.

when I play the keyboard, I only get some clicking sounds as I press the keys - which suggests that the midi is being received

I’ll post a pic when I get the chance. i suspect that there are several bad solder joints, but it would be useful to know where to start. No signal at Osc - so which board should I start with?

hi gabby. weird :wink: