11 Jun
2001
11 Jun
'01
6:16 a.m.
If you establish that the LM1881 can do this little job at the frequency at
which the monitor operates, please share details with me. I've used the LM1881
in the past, but only in connection with NTSC video.
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, June 11, 2001 11:27 AM
Subject: Re: sync on green to horizontal and vertical wiring seperator.
Hi!
This is getting frustrating.
This is fairly on topic because I run older Macs (1987 to 1991, and
many nubus video cards) that does not have native separate syncs by
design. I'm using a very dim Mac high resolution monitor. If
adjusted brighter, it will lose sharpness. It's already adjusted
perfectly and this doesn't helped. That's bad tube, caps that I can
check with my ESR are replaced already.
Before you give up, 2 checks..
1) Is the EHT voltage correct _and stable when you increase the
brightness_. You didn't mention the picture also got larger as the
brightness was turned up (a common symptom of EHT problems), but it's
still worth checking.
2) Try boosting the heater a bit. If there's a resistor in series with
the CRT heater, reduce it or short it out. If the heater supply comes
from its own regulator, try tweaking it up a bit. If you can do neither
of those, disconnect the existing heater supply and try running the
heater from 3 (or so) turns of wire wound round the flyback core. Every
6.3V CRT heater I've tried will stand 8V at least. This may not help, but
it might get you a couple more months out of an old CRT
But I might have one or two monitors I might able
to extract certain
IC to split the sync out to drive a peecee monitors which are in
plenty around here.
Otherwise if there a way to build that thing from scratch is nice.
Get the data sheet on the National Semiconductor LM1881 (or the Elantec
version that's a bit better). It's an 8 pin chip that's a video sync
separator. That should be able to pull the sync off the sync-on-green signal
(which after all is electically the same as a composite mono signal).
-tony