Well I guess it's my turn now... (Fried something something?)

Alright so eventually it would have been my turn to post on the forum for help.
So I’ve finally received my chips from LaurentideSynthworks and the PCB (gotta say the PCB looks awesome for those who are considering it) and I was so happy to put the final pieces to my already built Polivoks Shruthi.
MIRACLE! The LEDs works, switches respond. Only thing lacking is the led screen but first thing I notice is that the underneath of the filter board is super super hot. 2 minutes after trying to adjust the trim pot I hear the following :
"Pop"
And the Shruthi shuts down. :’(

Little panic moment. Realized I plugged some random Power supply and not my usual 9V pedal PSU I use for everything. Power supply used was/is DC 12V 800mA. Check the wiki and it isn’t so bad…right?

I have :

  • Checked with another completed filterboard (TubeOhm’s Shrutacon) to see if it’s the filterboard. Not the filterboard.
  • Checked the current path to see if I get 5V everywhere on the filterboards. All good.
  • Tried different psu. The one used is kaput. But the shruthi don’t respond to my 9V except for the Polivoks filterboard being super hot. But nothing on the mobo.

So, my question is, where can I check with a multimeter on the MOBO if the current is fine or not? Also, what is a good part to check first to see if it’s fried or not? (I got spares, fortunately) I thought it would be the 74hc595n since the joints looked darker than before but turns out that replacing it doesn’t change anything.

I’ll post pics tomorrow of the solder joints for troubleshooting’s sake.

If something gets hotter than normal, usually its a short. You may quote that.

I predict a short or bridge underneath the Display, probably from some debris.

Check the resistance between the +5V point and GND, on the control board and on the filter board.

Thanks for the tips. I was looking for a short but nothing. Still the pcb gets super hot around the PSU area but the heat goes down to around the regulators.
This being said, I checked the resistance on the digital board and it is around 140-150 which seems to be normal from what I’ve read on the forum. However, on both filterboards, I get nothing. But also, the headers are already soldered so I’m wondering if I’m doing a stupid rookie mistake here. This being said, I tried on the solder joints and still no resistance whatsoever between the GND and +5V.

Also, pictures (in case you see something that I don’t see)!

WELP, turns out it was the PSU that did the “poof” sound. My roomie noticed a diode looked more burnt than usual so I replaced it. Now I have a working Shruthi :smiley:
One thing though, the leds doesn’t respond anymore but the whole firmware does. I’m on it.

Other things :

  • Although I love distortion a lot (and it’s the main reason why I took the Polivoks filter), it seems like the sound is overdriven all the time to the point where the “overdrive” function doesn’t change anything.
    -Touching some joints on the back of the filterboard while a midi sequence plays changes the sound considerably. I guess that’s normal?

Does somebody has an example of how it supposed to sound with the init patch for a polivoks filterboard so I can actually determine if everything is normal or not? Would help me troubleshoot the whole thing.

I bet both problems are related - if the 74hc595 is fried, you won’t get any LED on and no filter/distortion routing data will be sent to the filter board.

One joint (top one) at least on the out expansion connector looks suspect.

What do you know, the 74hc595 was indeed fried. It plays perfectly now!
I even checked the joint for good measure and it’s good to go :smiley:

Now I just need to wait after that sweet Polivoks themed case I ordered from Altitude. Sadly, seems like USPS friggin lost it or it is stuck at the customs (with Harper, I wouldn’t be surprised if they think it’s some sort of communist bomb device enclosure or something…)