Analogue-sequencer

> and at the startup I'm getting "chk fail = 7d5c" and p3 stops

There are two programs in the P3 flash ROM.
The bootloader runs at power-on, checks to see if you are holding the keys
to trigger firmware update mode, then checks the main program is OK.
Then the main program is started.

Chk fail means the bootloader has found the checksum of the main program
does not match the stored checksum calculated when the main program was
first loaded.
You should be able to fix this by re-loading the main program.
That is, unless the power spike that seems to have caused corruption in the
main program also caused corruption in the bootloader.
The bootloader is only a small piece of code, so the chance of it being
corrupted if a random byte in ROM is lost is much smaller than for the main
program.
If the bootloader is damaged, the only fix is to send the CPU back to me for
brainwashing.

Best regards,
Colin Fraser
Sequentix Music Systems Ltd
http://www.sequentix.com