Retrofitting Maho MH600E 1989 - Meas 5i25 & 7i77

Not really, the 5I25 is only reset by a low 3.3V rail from the PC power supply

see Edit2

I would try another PC power supply, flashing red lights from the 5I25 most likely mean a bad ATX power supply (low 3.3V)

PCW wrote: I would try another PC power supply, flashing red lights from the 5I25 most likely mean a bad ATX power supply (low 3.3V)

as i said before, it´s not flashing and i´ve tried with a whole other computer.

The CR4 LED goes on and stays lit

OK if its only CR4 that's illuminated (not CR3 which is also red)
This may be a side effect of crashing, but if CR4 illuminates
and LinuxCNC is still running this means that the watchdog has bitten

If both CR3 and CR4 illuminate, that's a power issue

Debian corrupted: Unlikely
two out of three 5V PSU not suitable: Will not cause Linux to crash as long as you are not connected to and causing a problem with PC 5V
better grounding due common Poweroutlet: I suspect a grounding or EMI issue since every thing runs when not connected to the MAHO
corrupted mesa 5i25 firmware: Not really possible as its CRC checked and will not start if corrupted

The system crashes only with the scales connected. Maho doesnt even need to be powered. It only crashes when the 5V and 0V to the scales are connected.
The Mesa card seems to be ok. The Cr4 only burns when a crash has happened, or it has crashed until next start of linuxcnc.

Today i have changed the cables to shielded ones and could only improve the ttl signal now itś nice and crisp.
on the 5i25 the is a pinheader for 3.3V and GND. when i measure it with a multimeter it shows 3.3V
when i hook up my oscilloscope it shows something between 2,8V and XX. cant read due fast switching. Guess thatś ok too.

The most strange thing to me is still. that the pc ONLY crashes when LinuxCNC is running. iḿ writing from the linuxcnc pc now. its on for like 10 minutes.
when id start linuxcnc now. it would instant crash.

how can i see what linux does right at start that interacts with the encoders ?