27 Sep
2010
27 Sep
'10
11:32 a.m.
Excellent! This explains a lot. The CRT wasn't producing high
voltage when connected to the PET or when powered on stand alone. I do
believe it WAS producing high voltage when connected to the alto, hence
the video card on the alto should then be outputting signal! Make
sense, am I understanding your post correctly?
Yes, that sounds right.
The monitor need a horizontal sync/drive signal from the Alto for the HV
section to operate. Without it (for excample if the poniteir is powered
on its own), there will be bo high voltage.
This singal also needs to be the right frequency, which probably explains
wny it didn't work when connected to the PET
In fact driving it off-frequency could, I think, do damage, much as
plugging an IBM5151 MDA monuitor into a CGA card causes magic smoke to
escape.
-tony