New Hp9100A owner needs some repair help..

[jdreesen]

Short intro, as this is my first post here :
Jos Dreesen, from Switzerland, long time classic computer collector.

First "contact" with HP calcs : pressing my nose against a german shopwindow and longing for those jewels, totally out of reach for a 12 year old's pocketmoney. Hp35 ? 25 ? Don't remember..

Heavy HP41 user several years later.

Now retired, and stumbled upon a good find :
A HP9100A in very fine nick.
....with the memory expansion...and a printer....and a plotter....plenty magcards & full doku...

Allas marred by the fact that it does not work.

Checked so far : powersupplies OK, clocks ok. No display, internal statemachine ( ctl board with threader core rom ) does not seem to run..Where to start ? Tony had some suggestions that I will follow on, but happy to accept ideas from other s !

BR Jos