HP 8566B Spectrum Analyzer No Check Lights, Display Output or GPIB

[cestevens]

Hello all,

I recently got my hands on an HP 8566B Spectrum Analyzer.
Unfortunately it would appear the deal was too good to be true, as the instrument appears non-functional.
I've attempted to follow the troubleshooting guide, but I'm not sure where to go now with the information I have.

When powering, the CHECK INST I and II lights should go on, then power off.
Currently they never turn on in the first place, remaining off the whole time.
I think this would implicate something to do with the CPU board.
Accordingly the display unit and GPIB interfaces are unresponsive as well.
I haven't found any part of the manual that describes what to do continuing from here.

I have attempted reseating all the boards I can.
The regulated voltage lines all seem okay, unregulated are generally a little further out but within what I guess to be reasonable.

If anyone knows what I ought to try next I would appreciate it.

[m k]

Not exactly very simple device.

No LEDs ever can also mean that power is not connected further.
Standby LED(DS1) should be on when machine is in standby state.
Somewhere is also an overtemp sensor.