Holy crap, I've spent about 24h. (OK well at least a good part of it) between despair and regret....
Story is....my 9100A's front has come loose. That plastic of the front has become rather brittle over the years and the "latches" (or clamps or whatever they are called) had been partially broken, probably from people opening it before I owned it.
Now, I had put away the machine somewhere but somehow the complete front had fallen down from about 1 meter...... I was not really that worried about it, the flat cable had come loose of course, but I had checked the pins right away and they were not even a bit bent...
But......the display in this unit is not an LED or LCD device but a VFD (Vacuum Fluorescent Display).
(
https://www.youtube.com/watch?v=clUVEyi_YNM )
Essentially this is a bit like a CRT (although still different) but it IS in essence a glass tube...soooooo.... there was a slight worry about it...
I wanted to see if I could check some things on the Asteroids so I got out the unit, reconnected the front and powered it up......
The display remained dark and my heart sank.... The LED indicators for BUSY and Hard Drive activity were still working so the connector was OK. Keyboard worked too (at least, I could reset the unit with the reset key).
I tried reseating the Z8 processor as it was somewhat loose, but that didn't help. And there's not much more that can come loose on the display PCB so I thought I was screwed.
You see these displays are not available anymore. There are still VFD's being made, but not this type....
So I already started looking around/asking if anyone would have a display....but the search was unsuccesful.
I already started to look at how the unit sends data to the display (basic enough, ASCII characters as RS-232 at TTL level, but there is also some special graphic commands) and if it might be possible to use another display.
However....as always.....check basics. What bothered me was that there was no visual damage on the VFD. No breaks or cracks. The slightest crack would render it useless of course, because the vacuum has to remain in tact for it to not burn out....
So....let's check voltages ! The VFD requires a couple of rather strange voltages, one of them is 70V for the filament. Measured that one first and....nothing !
Mmmmm....so I searched through the schematics, couldn't find anything how the 70V was generated but I _did_ find a repair log (
http://www.jammarcade.net/fluke-9100-repair-log/ ) and there it mentioned a 125mA fuse for the 70V. I had seen a fuse quite near the front of the unit so.....let's see. Measure it: open !
Replaced it and.....
YESSSSSSSS I was greeted by the beautiful glow of the VFD again ........MAN was I HAPPY !!!!!!!!!
