Shruthi picks up alien messages (troubleshooting)

I thought my shruthi (lp2+delay) doesn’t work after I replaced display, there was nothing shown on display. Today I incidentally made it work by randomly tweaking pots. What I’ve found out: shruthi works normally (delay works too) until I tweak third or fourth pot. If I do so, shruthi freezes then this comes up on display + sometimes some random signs, also shruthi emits noise similar to the one when you select wrong filterboard in the settings. After that the only way I can make it behave normal again is by tweaking pots. Strange… Alien interference or something else? Any ideas?

Your Shruthi is possessed by an Alpha Juno. May Roland have mercy on your soul. Although that is the Korg filter type. :slight_smile:

Maybe it’s shorting something under the display.
Try to raise the LCD a bit and try to recall the freeze.

I checked very carefully, there are no shorts, all solder points seem fine. I think some chip must be bad… I found out this guy has similar problem with shruthi in another thread My shruthi freezes too, and sometimes when I power it only LEDs 1-7 light up. Then I plug it in&out couple of times and tweak some pots and it works again. Is there any way to check if any chip is bad (74hc595, 165…)?

Check that one of the IC pins hasn’t folded underneath the chip. It will work for a while but then make intermittent connections when moved or warming up.

I checked the ICs, no folded pins. This shruthi was already working, then I replaced LCD with an OLED. I bridged the pins where the 68 ohm LCD resistor goes, could this cause a short of some sort? On my working shruthi I left it out…

With an OLED you can leave the resistor for the becklight intensity open, but I don’t see how bridging it is going to be related to these issues. You need input on one of the not-connected data lines to get the characters that are being displayed. If you are certain that there are no solder bridges on the connector for the LCD, I suspect the display itself may be faulty…

No there are no solder bridgeson the connector. Well I am thinking about the resistor because I wanted to remove the lead, and I ripped a pad from one pin at LCD 68-ohm resistor that is on the trace that goes to midi connector. So does pulling a pad out stop the current thorugh the trace?

Also, another problem… I tried connecting my other control board to lp2+delay and digi/fx filters. Lp2+delay filter is ok, but digital/fx filter emits a lot of noise, almost as loud as the signal (although all functions work). Digital filterboard is my favorite :slight_smile: Where could the noise come from? Only mistake I made at building was I used stock mcp4921 chip that I bought, I didn’t realize it comes with filter preprogrammed. As soon I realized the mistake I replaced it.

4921 doesn’t need programming.

Yes, of course you are right, I swapped 4921 again and there’s no difference, my bad. Here is digital/fx shruthi sample (into focusrite scarlett=>ableton): wav ? I like noise but is this normal?

I think I was “a bit” overreacting, there’s not much noise, digital/fx board is ok :slight_smile: now I’ll try to repair control board… is it posible to sand or scratch a bit of pcb and solder a wire to the exposed trace? can’t find anything useful about such repair on the internet…

As all traces go from one part to another its a way better idea to identify which pin at which part is connected and run a flying wire instead of trying to scratch away the silkscreening (which is specifically designed to be nonscratchable :wink: ) and possibly damaging something else.