11 Jun
2001
11 Jun
'01
6:03 a.m.
From: ard(a)p850ug1.demon.co.uk (Tony Duell)
Subject: Re: sync on green to horizontal and vertical wiring seperator.
To: classiccmp(a)classiccmp.org
Date: Mon, 11 Jun 2001 18:27:07 +0100 (BST)
Reply-to: classiccmp(a)classiccmp.org
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.
No expanding when I change brightness, very stable. But items would
grow colorful trails to the right if I broost too much gain or screen
on each gun, it has set of 2 pots for each R, G, B guns. But this is
not the problem apprently.
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
I'll try that. I already have traced the wiring for that heater, it
leads directly from fly to the heater. I think there is a disc cap
and a resistor. Have to open it up and look again. It's very
service-friendly monitor, RF shield snaps off to expose the CRT
board, main board swings out on pair of plastic hinges. Well built
monitor, heavily shielded. Only difference on this monitor both
screen and focus is on seperate circuit board not on fly itself.
Doesn't the heater demands lot of current flow?
Doesn't this monitor can be affected by too low voltages for B+
power?
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