1 Dec
2013
1 Dec
'13
6:27 p.m.
On Sunday (12/01/2013 at 04:18PM -0500), rescue wrote:
Been a while since I worked on CRTs on my video games... but IIRC if
the HV drops the picture will bloom as the yoke can deflect the beam
further before the electrons strike the face. If your picture is
sharp but dim, my first guess would not be an HV problem. When I
was working on my arcade games, I picked up for a pretty good price
a voltage probe for CRTs.
Have you measured the filament voltage to the CRT ? not sure what
VT220s would be, but I IIRC on arcade stuff is is I think 6.3V.
Are you able to easily swap a tube to see that the dim problem
follows the electronics and not the tube ?
yes! Thanks Curt. I did swap the tube after posting the message and sure
enough, it was the tube after all. With a new tube, (see my messages
from a couple weeks ago where we saved NOS tubes from
the scrapper!) it
works like a charm.
So, I'm sure Tony will be all over me for swapping stuff before measuring
stuff but in this case, it panned out pretty well :-)
Would still like to find prints for this newer VT220 design but can move
forward now without them.
Chris
--
Chris Elmquist