1 May
2005
1 May
'05
4:44 p.m.
Hello fellow ClassicCmp'ers,
I have a Viewsonic PT813 21" CRT monitor, a very high-end professional model
that I was told used to cost $1800 new (1997), has both DE15 and BNC inputs
and supports both PeeCee video and sync on green. Unfortunately it is
malfunctioning - the picture is smudged to the point of being totally
unreadable. It seems like some component in its circuitry went bad -
I don't think it's the CRT - so it's probably fixable.
The person who sold it to me has agreed to refund me what I paid for it
and let me keep the broken monitor, and OKed me offering it for free to
the list. Since I believe it to be fixable, but lack the time, tools and
skills necessary to do so, I offer it for free to anyone who thinks he can
fix it.
If fixed it would make a great monitor for classic computers, and has the
added bonus that the VS3100 GPX board firmware is perfectly happy with this
monitor connected (as I wrote in my other posts, it often throws up a tantrum
with other perfectly good SoG monitors). So if you fix it, it should work
beautifully with VS3100 GPX, VS3100 SPX, other DEC and other classic
workstations.
The monitor is near San Diego, California. If you want it, you must come
and pick it up. I lack the materials and skills to properly pack it for
shipping (if I shipped it, you would get a pile of broken plastic and glass
instead of a bad-but-fixable monitor), and I don't even have a car to take
it to a shipping store that could pack it for me.
MS
2 May
2 May
10:55 a.m.
I have a Viewsonic PT813 21" CRT monitor, a very
high-end professional model
that I was told used to cost $1800 new (1997), has both DE15 and BNC inputs
and supports both PeeCee video and sync on green. Unfortunately it is
malfunctioning - the picture is smudged to the point of being totally
unreadable. It seems like some component in its circuitry went bad -
I don't think it's the CRT - so it's probably fixable.
A word of warning to anyone who gets this... I had an Apple Mac+ that had
a smeared display -- shaddows to the right of objects on the screen. Now,
the Mac+ video circuit is pretty simple, but none-the-less I spent quite
a time going through it, unable to find the fault.
The reason I couldn't find a fault in the video amplifier was that there
wasn't one. It was the CRT. Low emission, I think.
Most of the time, a smeared picture _is_ a fault in the video amplifier,
though. But it may not be.
-tony
12:59 p.m.
Tony wrote:
Most of the time, a smeared picture _is_ a fault in
the video amplifier,
though. But it may not be.
It can also be caused by use of a cheap video cable or a cheap KVM switch.
(Note that I deliberately used the word "cheap" rather than
"inexpensive".
I've seen expensive video cables and KVMs that were "cheap", and
inexpensive ones that were not "cheap".)
1:25 p.m.
Tony Duell wrote:
A word of warning to anyone who gets this... I had an
Apple Mac+ that had
a smeared display -- shaddows to the right of objects on the screen. Now,
the Mac+ video circuit is pretty simple, but none-the-less I spent quite
a time going through it, unable to find the fault.
The reason I couldn't find a fault in the video amplifier was that there
wasn't one. It was the CRT. Low emission, I think.
Most of the time, a smeared picture _is_ a fault in the video amplifier,
though. But it may not be.
I had a trintron tube connected to the same computer for 8 years slowly go
"smeary" on me and I never found out why (monitor was on for only 3-4 hours
each day, not 24/7). The "smears" were always after a high-to-low or
low-to-high contrast (ie biggest voltage change) on the screen and were always
in the direction of the scan (ie left to right, eventually fading out at the
far right). Video card never failed once, and produced a perfect picture on a
new monitor.
So what caused that? What went "bad" over time to cause such a thing, and is
it fixable?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Want to help an ambitious games project? http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
4:35 p.m.
On Mon, 2 May 2005 18:55:08 +0100 (BST)
ard at p850ug1.demon.co.uk (Tony Duell) wrote:
The CRT on a Mac Plus is probably one of the easiest video tubes to
replace. It's nice and small, and it's not many screws to get a Plus
apart enough to swap it. I'm not sure that (used) replacement CRTs are
as plentiful as they were five years ago when I replaced one, though.
There used to be Apple-oriented 'scrap' shops where you could get a
pulled tube for ten dollars.
I have a
Viewsonic PT813 21" CRT monitor, a very high-end
professional model that I was told used to cost $1800 new (1997),
has both DE15 and BNC inputs and supports both PeeCee video and sync
on green. Unfortunately it is malfunctioning - the picture is
smudged to the point of being totally unreadable. It seems like
some component in its circuitry went bad - I don't think it's the
CRT - so it's probably fixable.
A word of warning to anyone who gets this... I had an Apple Mac+ that
had a smeared display -- shaddows to the right of objects on the
screen. Now, the Mac+ video circuit is pretty simple, but
none-the-less I spent quite a time going through it, unable to find
the fault.
The reason I couldn't find a fault in the video amplifier was that
there wasn't one. It was the CRT. Low emission, I think.
3 May
3 May
3:48 p.m.
The CRT on a Mac Plus is probably one of the easiest video tubes to
replace. It's nice and small, and it's not many screws to get a Plus
The other advantage is that it's a monochorme CRT, so there's little
setting up to do....
Most people here won't have had to set up a delta-gun colour CRT from
scratch, but there's about 20 adjustmets, many of which interact. I had
to do the one in my Barco TV monitor which had been 'repaired' by its
previous owner. After sorting out the EHT regulator, the kludges to the
convergence board, etc, I then had to set everything up...
-tony
7125
days inactive
7127
days old
5 comments
5 participants
participants (5)
-
ard＠p850ug1.demon.co.uk -
chenmel＠earthlink.net -
eric＠brouhaha.com -
msokolov＠ivan.Harhan.ORG -
trixter＠oldskool.org