Help - I think I killed my Anushri

I’m in the process of Euroracking my Anushri. Desoldered the MIDI and audio connectors, soldered the 5-pin connector, removed the DC-DC converter and connected the whole thing to a Meanwell PSU from Reichelt. I carefully measured beforehand to make sure 12v, 12v and GND were laid out correctly. When I switched everything on, all the LEDs came on at once and stayed on - something went wrong, obviously. So I took the Anushri off the PSU, put the DC-DC converter back in and tried with a 9V power supply again. Now even with that, all the LEDs come on and stay on.

I haven’t resoldered the MIDI and audio jacks yet, could that be the problem? Otherwise, can someone help me debug this? I really don’t know what I did wrong.

Not touching the MIDI and AUDIO jacks won’t cause any problem if it worked before.

Are you sure you plugged in the Eurorack Power connector correctly? According to the schematics theres only reverse voltage protection for the 9V power in….
If reversed you may have killed your Regulators, first thing to check is Voltages on the main board.

Use this Picture from the Building Instructions as reference, in this Pic Blue is GND, RED is +5V, Green is -5V

I’m pretty sure I did not reverse polarity, but it looks like I did damage something. The red points in the “power distribution” section of the build instructions all measure +10V instead of +5V. I hope I did not fry all the ICs.

What Power Supply do you use, the 9V Wallwart or a ±12V Eurorack?

What about the negative -5V Rail?

First thing i would do is remove all chips, replace the 7805, check for shorts, power up and measure again. At +10V you surely have fried the ATMega and probably some of the Logic Chips, too. The V2164 is also sensible to asymmetric Rails and is suspectible to be dead but before troubleshooting this you have to make sure your Power is OK

OK I did replace the 7805. Now the power supply looks OK, measured all points and they all have the correct voltages. It does look like I fried the ATMega though; probing it with an ISP programmer yielded a device signature of 0…

I didn’t have any ATMega328Ps in stock so I temporarily relieved one of my Ambika’s voice boards of its one. This one reacted to the ISP, so I flashed it with the Anushri firmware and re-populated first the logic chips. Powering on showed sensible behavior for the LEDs, buttons and LFO speed knob. So I re-populated the chips for the analog chain, and now I get drum sounds and synth sounds again. Looks like I did not fry a lot more – phew! I will only really know after I re-solder the MIDI sockets, but right now I think I got away with a scare.

I am still sure I never reversed polarity on the -12V/+12V power supply. Here is what I think what happened. When I first built up the Anushri, I stupidly soldered the 7805/7905 the wrong way, heat sinks toward the center of the board. I powered up, no sound, so I double checked, found the mistake and re-soldered the voltage controllers the right way. Everything worked after that so I didn’t worry. I think using the other power supply was the straw that broke the camel’s back.

Thank you very much for your help, fcd72!

Ah, that wasn’t much of a help, just a bit keeping calm…. and you have found a good explanation yourselves. Pay attention that the Regulators heatsink doesn’t accidentally touch anything, else you will have to start over again :wink: