Some time ago I posted asking for help with my VT100 monitor board and
flyback. This is the monitor board that uses Germanium transistors and
for which there is no known printset available. The conclusion was that
the flyback had failed, proved by the burning smell and poor ring test
results, and described at greater length here;
https://robs-old-computers.com/2026/03/30/vt100-video-display-failed-flybac….
I have managed to get a NOS replacement flyback. The ring test shows
that it is good. However, I have enough suspicions about the two
Germanium transistors (Q414 and CR406) that I don't want to just slap it
in and hope it works, especially as I have little chance of ever finding
another flyback. The primary coil of the flyback, driven by these two
transistors, is the one that is shorted in the bad flyback and I don't
know if the flyback failed because of these transistors or not.
Are there any tests I could do on the monitor board prior to fitting the
new flyback? Could I source any kind of modern inductor to act as a
sacrificial part that would be enough to prove correct operation?
I have updated my own reverse engineered schematic
here:
https://robs-old-computers.com/wp-content/uploads/2026/09/5414131-partial-s….
This is from a KiCad 10 schematic and I can of course supply that if it
would help.
Thanks
Rob