18 Nov
2010
18 Nov
'10
9:14 p.m.
Hi all,
I suspect some folk here have done this before.... :-)
Indeed. But be warned modern CRTs (and 10 years old is 'modern') don't
necessariy respond to this.
My desktop CRT (over 10 years, but not what I'd consider vintage!) has been
ailing for some time, with the picture getting darker and darker despite
having the brightness at 100%. It's still good for high-contrast stuff such as
black text on white background, but forget trying to pull details out of most
photos, for instance.
before you go any further, have you checked all the CRT voltages? I guess
you didn't do what I do, and measure/record them when the unit is new, so
as to have somethign to compare against. But you might be able to spot
any that are way out...
Is there any colour cast? The reason I ask is that it's unusual for all 3
cathodes to loose emision together, so normally one primary colour will
fade first. if the colours are still fine, I would not try to boost the
heater.
Have you tried a cautious tweak of the g2/screen control (often on the
flyback transformer)?
Heater voltage seems good at 6.4VDC / 350mA (it's derived from the PSU in this
monitor rather than the flyback section), but I'm considering boosting it a
little and see if it improves things, obviously shortening the life of the
tube in the process.
Question is, what's a sensible amount to over-run things by? Say I aimed for
around 10%, is that too much and going to kill the heaters in next to no time,
or so little that unlikely to really make any useful difference?
Normally around 10% will do someting. I've taken 6.3V heaters up to 10V
(!) for rejuvenating the CRT (not the same thing) but only for a few
minutes. Certainly running them at 7V or so should show some improvement
_if the emission is the real problem_.
-tony