I acquired several VaxStations 4000/90. Some of them power up to console but some of them remain unresponsive with all LEDs lit.

The manual says that this error means: Power has been applied but no instruction has been run. Replace the System module (i.e. mainboard).

I confirmed the above-mentioned by swapping other parts (PSU, RAM, framebuffer) from working VaxStations.

Since I have several machines showing the same error, it seems that there may be some common cause.

Any idea where to start looking for a solution?