KA640 CPU no operation - "F" on Console Panel

[spiceminer]

Dear All,

I have recently got a Microvax 3400 in nice condition. Unfortunately is the KA640 CPU board stuck in "F" condition (LED on Console Panel)
with no output on the serial console.

Anybody maybe some ideas?

 

[MattisLind]

Are your DC OK and POWER OK signals generated correctly by the power supply? Those signals are usually used for resetting the machine.

 

[spiceminer]

Are your DC OK and POWER OK signals generated correctly by the power supply? Those signals are usually used for resetting the machine.

I assume so. A KA650 CPU works fine in the same enclosure. Both PWR OK LEDs of both power supplies are on.