Hi Ben,
the news: Came into the workshop this morning and plugged the VCR into
mains.
VCR came up immediately and worked fine.
I think, I should not understand this yet. Life is too short ;-)
At this time I assume static charge at the DEW input of the
control-processor. I have no schematic to verify this.

In my last post I had an error. The unused connector is marked 'DW'.
Seems to be for an DEW sensor.

Let's hope the VCR will work the next days so I can return it to the
customer.

73
Peter

ps.: In the past I also had stuck buttons. This failure also occured
when front panel removed.