B&W monitor - dim picture

C

Chris

Guest
I have a 1995 vintage closed circuit television monitor which is
probably from some kind of a security system.

It has a very dim picture. The picture looks ok, but I can
only see it if the contrast and brightness are maxed out
and the room lights are low.

I found an adjustment marked "sub bright" and fiddled with
that. The picture didn't seem to get any brighter overall,
but the blacks got "white" and the whites got wierd, kind
of like a photographic solarization look. There are 4 video
inputs, and the screen can alternate between a single and a
quad view. It doesn't seem to matter which input I use.
The subtitle dates, etc. are all dim too.

My question is: is it likely there is just an out-of-spec
resistor in there somewhere? or is it a slam dunk
that the tube is shot? If there is a reasonable chance to
resurrect the thing I'd like to know before I spend a lot
of hours on it. Otherwise I'll put it in the pile
to cannabalize for other projects.

If it helps, the picture tube says Samsung 440CWB4(Q).
 
kc0atc@qsl.net (Chris) wrote:
I have a 1995 vintage closed circuit television monitor which is
probably from some kind of a security system.

It has a very dim picture. The picture looks ok, but I can
only see it if the contrast and brightness are maxed out
and the room lights are low.
Click to expand...
You don't mention any of the history of this screen. If it's been
switched on for the bulk of the time since 1995 (quite probable for a
security camera screen) then it's likely the tube is shot. Bin it.


Tim
--
The .sig is dead.
 
Chris:
Based on your description of the symptoms "it is a slam dunk that the tube
is shot"
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
----------------------


"Chris" <kc0atc@qsl.net> wrote in message
I have a 1995 vintage closed circuit television monitor which is
probably from some kind of a security system.

It has a very dim picture. The picture looks ok, but I can
only see it if the contrast and brightness are maxed out
and the room lights are low.

I found an adjustment marked "sub bright" and fiddled with
that. The picture didn't seem to get any brighter overall,
but the blacks got "white" and the whites got wierd, kind
of like a photographic solarization look. There are 4 video
inputs, and the screen can alternate between a single and a
quad view. It doesn't seem to matter which input I use.
The subtitle dates, etc. are all dim too.

My question is: is it likely there is just an out-of-spec
resistor in there somewhere? or is it a slam dunk
that the tube is shot? If there is a reasonable chance to
resurrect the thing I'd like to know before I spend a lot
of hours on it. Otherwise I'll put it in the pile
to cannabalize for other projects.

If it helps, the picture tube says Samsung 440CWB4(Q).
Click to expand...
 
You are giving the common description of a tube being warn out. The monitor
is a bit old. To check the performance, you can take voltage readings and
measure the waveforms to the elements of the tube and verify them to the
service manual.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Chris" <kc0atc@qsl.net> wrote in message
news:a444e1b1.0401221927.7e818525@posting.google.com...
I have a 1995 vintage closed circuit television monitor which is
probably from some kind of a security system.

It has a very dim picture. The picture looks ok, but I can
only see it if the contrast and brightness are maxed out
and the room lights are low.

I found an adjustment marked "sub bright" and fiddled with
that. The picture didn't seem to get any brighter overall,
but the blacks got "white" and the whites got wierd, kind
of like a photographic solarization look. There are 4 video
inputs, and the screen can alternate between a single and a
quad view. It doesn't seem to matter which input I use.
The subtitle dates, etc. are all dim too.

My question is: is it likely there is just an out-of-spec
resistor in there somewhere? or is it a slam dunk
that the tube is shot? If there is a reasonable chance to
resurrect the thing I'd like to know before I spend a lot
of hours on it. Otherwise I'll put it in the pile
to cannabalize for other projects.

If it helps, the picture tube says Samsung 440CWB4(Q).
 
On 22 Jan 2004 19:27:31 -0800, kc0atc@qsl.net (Chris) wrote:

but the blacks got "white" and the whites got wierd, kind
of like a photographic solarization look.
Click to expand...
It's a slam dunk the tube is bad. The classic 1950's textbook
description of a weak tube is "The whites turn silvery without any
increase in brightness."

. Steve .
 
Tim Auton <tim.auton@uton.[group sex without the y]> writes:

kc0atc@qsl.net (Chris) wrote:
I have a 1995 vintage closed circuit television monitor which is
probably from some kind of a security system.

It has a very dim picture. The picture looks ok, but I can
only see it if the contrast and brightness are maxed out
and the room lights are low.

You don't mention any of the history of this screen. If it's been
switched on for the bulk of the time since 1995 (quite probable for a
security camera screen) then it's likely the tube is shot. Bin it.
Click to expand...
Last resort: boost the CRT filament voltage 10 or 20 percent and see
if that helps.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the feedback form on the S.E.R FAQ Web sites.
 
Sofie (sofie@olypen.com) wrote:
: Chris:
: Based on your description of the symptoms "it is a slam dunk that the tube
: is shot"

I wouldn't bet the farm on it.

Although it's possible the tube is bad, I've worked on a number of cc
monitors like GBC and the symptoms can point to bad caps.

Before you toss it, eyeball the chassis and see if there are any caps with
odd values, like 47uf @350v, not the mylar ones, the electrolytics. Usually
have high voltages, 1uf@160v is another one (also 3.3@160v).

They have come up with some weird circuits in those things for sync
separators and video coupling. I'd try to replace the 3 or 4 oddballs and
cross your fingers.

Even though they may have been in use for 10 years, those usually aren't
standard picture tubes in those things. They go bad but not as often as
regular tv's. Burn-in is far more common than weak tubes.

One other thought, just for yucks also check the neck assembly for high
value resistors (270k, 330k), these too, if they open can cause a gassy pix.

-bruce
bje@ripco.com
 
"Steve(JazzHunter)" <jazzhunterNotHere@internet.com> wrote in message
news:sfl110pufmlk975rgibiiehkj6i4a0e2kc@4ax.com...
On 22 Jan 2004 19:27:31 -0800, kc0atc@qsl.net (Chris) wrote:

but the blacks got "white" and the whites got wierd, kind
of like a photographic solarization look.

It's a slam dunk the tube is bad. The classic 1950's textbook
description of a weak tube is "The whites turn silvery without any
increase in brightness."

. Steve .
Click to expand...
The tube is bad, the contrast switch doesn't work, so you MUST sell this on,
where else?, eBay!
Here's a possible listing you can try:

"Vintage, mid-90's, rugged computer monitor, B&W, works good! Useful
for home or office security systems, camera not included!
Minimum bid - $40 (not including shipping) OR
Buy it NOW - $35"

Damn, now that's marketing!!
 
"Bob F." <bobf@phantom.com> wrote in message
news:40118865$0$43850$39cecf19@news.twtelecom.net...
"Steve(JazzHunter)" <jazzhunterNotHere@internet.com> wrote in message
news:sfl110pufmlk975rgibiiehkj6i4a0e2kc@4ax.com...
On 22 Jan 2004 19:27:31 -0800, kc0atc@qsl.net (Chris) wrote:

but the blacks got "white" and the whites got wierd, kind
of like a photographic solarization look.

It's a slam dunk the tube is bad. The classic 1950's textbook
description of a weak tube is "The whites turn silvery without any
increase in brightness."

. Steve .

The tube is bad, the contrast switch doesn't work, so you MUST sell this
on,
where else?, eBay!
Click to expand...

I wouldn't give up completely yet, at least check to see if the contrast
control circuitry is working, it *could* be just an open resistor, I agree,
probably the tube, but worth spending a few minutes to find out.
 
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