[Premium-Rx] Help needed with Hagenuk RX1001M

[Heinz Breuer]

Hello,
after a couple weeks on the shelf my Hagenuk RX1001M does not start anymore.
After switching power on all LEDs are lit and nothing else happens.
It seems that the microprocessor is not running the startup sequence?

This receiver has extensive BITE but I can't even access the BITE sequence.
I apprecaiate any help where to start trouble shooting.

vy 73 Heinz DH2FA, KM5VT