Ok, back home with unit now. Let's see what we are dealing with..
Steel chassis is rusty on rear side. Not nice treatment for such an instrument.
Removing covers...
All analog stuff is contained in aluminum box, isolated from steel frame by plastic inserts. HP calls those boards inside as "inguard", rest boards are "outguard".
View on both sides without covers. As we can see, no A9 voltage reference present
Inguard PSU. Some PCB damage around CR12 visible.
Outguard primary PSU. All seems ok.
68000 CPU, RAM, ROM and digital logic, board A5. Dated 1990, while rest of analog PCBs dated 1996.
Probably seller changed digital PCB afterwards?
Removing inguard PSU for now, adding jumpwire instead of fuse (don't have suitable cap), turning on...
Aha. Nice and bright VFD, which is cool. Now will remove Dallas NVRAMs , and solder sockets instead, so we can troubleshoot this RAM 1 LOW.