I've had this Viewsonic PF790 19" CRT monitor for quite a few years now and
it has been used daily since it was new without any issues. Recently I have
noticed that large white images will cause the horizontal size to shrink
about 1cm overall. I keep my desktop set to black so if I minimize a window
I see the picture expand or if I open a window I see the picture shrink. It
is possible that it has always done this, but I don't believe that it has.
Any thoughs on what might be going out?

Mike

"Michael Kennedy" wrote in message
. ..
I've had this Viewsonic PF790 19" CRT monitor for quite a few years now
and it has been used daily since it was new without any issues. Recently I
have noticed that large white images will cause the horizontal size to
shrink about 1cm overall. I keep my desktop set to black so if I minimize
a window I see the picture expand or if I open a window I see the picture
shrink. It is possible that it has always done this, but I don't believe
that it has. Any thoughs on what might be going out?

Mike


I just set my monitor to 100hz, the setting I used to keep it at. With a
mostly black picture the desktop streches beyond the edges of the screen and
is dark and slightly purple. I guess I have some issue in the horizontal
deflection circuitry. I'm a novice at PC monitors so any suggestions would
be great.

"Michael Kennedy" wrote in message ...

"Michael Kennedy" wrote in message
. ..
I've had this Viewsonic PF790 19" CRT monitor for quite a few years now
and it has been used daily since it was new without any issues. Recently I
have noticed that large white images will cause the horizontal size to
shrink about 1cm overall. I keep my desktop set to black so if I minimize
a window I see the picture expand or if I open a window I see the picture
shrink. It is possible that it has always done this, but I don't believe
that it has. Any thoughs on what might be going out?

Mike


I just set my monitor to 100hz, the setting I used to keep it at. With a
mostly black picture the desktop streches beyond the edges of the screen and
is dark and slightly purple. I guess I have some issue in the horizontal
deflection circuitry. I'm a novice at PC monitors so any suggestions would
be great.

No one needs a refresh rate that high. Set it to something
reasonable (e.g. 75 or 85Hz) and see if that helps.

Michael Kennedy wrote:

I've had this Viewsonic PF790 19" CRT monitor for quite a few years now and
it has been used daily since it was new without any issues. Recently I have
noticed that large white images will cause the horizontal size to shrink
about 1cm overall. I keep my desktop set to black so if I minimize a window
I see the picture expand or if I open a window I see the picture shrink. It
is possible that it has always done this, but I don't believe that it has.
Any thoughs on what might be going out?

Large white images require more current.

Clearly the supply voltage for that part of the circuitry is sagging under the
additional current demand. A PSU problem.

Graham

writes:

"Michael Kennedy" wrote in message ...

"Michael Kennedy" wrote in message
. ..
I've had this Viewsonic PF790 19" CRT monitor for quite a few years now
and it has been used daily since it was new without any issues. Recently I
have noticed that large white images will cause the horizontal size to
shrink about 1cm overall. I keep my desktop set to black so if I minimize
a window I see the picture expand or if I open a window I see the picture
shrink. It is possible that it has always done this, but I don't believe
that it has. Any thoughs on what might be going out?

Mike


I just set my monitor to 100hz, the setting I used to keep it at. With a
mostly black picture the desktop streches beyond the edges of the screen and
is dark and slightly purple. I guess I have some issue in the horizontal
deflection circuitry. I'm a novice at PC monitors so any suggestions would
be great.

No one needs a refresh rate that high. Set it to something
reasonable (e.g. 75 or 85Hz) and see if that helps.

If it used to work and is within the specs of the monitor scan rate, then
that's not the issue.

Something is failing in the deflection or power supply, and the regulation
is suffering.

--- sam | Sci.Electronics.Repair FAQ: 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 Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Effect is called "Blooming" and is directly related to the power supply
circuits not able to supply the additional current required to display the
brighter raster, you will also notice a slight de-focus of the information
when the screen decreases in size.
Eeyore" wrote in message
...


Michael Kennedy wrote:

I've had this Viewsonic PF790 19" CRT monitor for quite a few years now
and
it has been used daily since it was new without any issues. Recently I
have
noticed that large white images will cause the horizontal size to shrink
about 1cm overall. I keep my desktop set to black so if I minimize a
window
I see the picture expand or if I open a window I see the picture shrink.
It
is possible that it has always done this, but I don't believe that it
has.
Any thoughs on what might be going out?

Large white images require more current.

Clearly the supply voltage for that part of the circuitry is sagging under
the
additional current demand. A PSU problem.

Graham

Sam Goldwasser wrote in
:

writes:

"Michael Kennedy" wrote in message
...

"Michael Kennedy" wrote in message
. ..
I've had this Viewsonic PF790 19" CRT monitor for quite a few
years now and it has been used daily since it was new without any
issues. Recently I have noticed that large white images will
cause the horizontal size to shrink about 1cm overall. I keep my
desktop set to black so if I minimize a window I see the picture
expand or if I open a window I see the picture shrink. It is
possible that it has always done this, but I don't believe
that it has. Any thoughs on what might be going out?

Mike


I just set my monitor to 100hz, the setting I used to keep it at.
With a mostly black picture the desktop streches beyond the edges
of the screen and is dark and slightly purple. I guess I have some
issue in the horizontal deflection circuitry. I'm a novice at PC
monitors so any suggestions would be great.

No one needs a refresh rate that high. Set it to something
reasonable (e.g. 75 or 85Hz) and see if that helps.

If it used to work and is within the specs of the monitor scan rate,
then that's not the issue.

Something is failing in the deflection or power supply, and the
regulation is suffering.

my guess would be electrolytic caps,bad ESR.
You MUST use low-ESR,105degF caps for replacements.

Not a task I'd suggest for a neophyte,I suggest buying a new LCD monitor.

--
Jim Yanik
jyanik
at
kua.net

With the ageing of the monitor, the power supply regulation and scan
circuit stability has decreased. The most common cause are electrolytic
capacitors going high in ESR. If all the capacitors in the monitor were
to be checked with an ESR meter, there is a possibility of finding many
of them out of specs. This may not be a feasible repair for a monitor as
old as the one that you have.

--

Jerry G.


"Michael Kennedy" wrote in message
. ..
I've had this Viewsonic PF790 19" CRT monitor for quite a few years now
and
it has been used daily since it was new without any issues. Recently I
have
noticed that large white images will cause the horizontal size to shrink
about 1cm overall. I keep my desktop set to black so if I minimize a
window
I see the picture expand or if I open a window I see the picture shrink.
It
is possible that it has always done this, but I don't believe that it
has.
Any thoughs on what might be going out?

Mike

"Jim Yanik" wrote in message
...
Sam Goldwasser wrote in
:

writes:

"Michael Kennedy" wrote in message
...

"Michael Kennedy" wrote in message
. ..
I've had this Viewsonic PF790 19" CRT monitor for quite a few
years now and it has been used daily since it was new without any
issues. Recently I have noticed that large white images will
cause the horizontal size to shrink about 1cm overall. I keep my
desktop set to black so if I minimize a window I see the picture
expand or if I open a window I see the picture shrink. It is
possible that it has always done this, but I don't believe
that it has. Any thoughs on what might be going out?

Mike


I just set my monitor to 100hz, the setting I used to keep it at.
With a mostly black picture the desktop streches beyond the edges
of the screen and is dark and slightly purple. I guess I have some
issue in the horizontal deflection circuitry. I'm a novice at PC
monitors so any suggestions would be great.

No one needs a refresh rate that high. Set it to something
reasonable (e.g. 75 or 85Hz) and see if that helps.

If it used to work and is within the specs of the monitor scan rate,
then that's not the issue.

Something is failing in the deflection or power supply, and the
regulation is suffering.

my guess would be electrolytic caps,bad ESR.
You MUST use low-ESR,105degF caps for replacements.

Not a task I'd suggest for a neophyte,I suggest buying a new LCD monitor.

--
Jim Yanik
jyanik
at
kua.net

Well it's not my first time working on a CRT, but I just don't have tons of
expirence. I've fixed minor things in TV's before, cold solder joints, etc.
I have an ESR meter so with a little time I should be able to find the
suspect caps.

"AJ" wrote in message
. ..
Effect is called "Blooming" and is directly related to the power supply
circuits not able to supply the additional current required to display the
brighter raster, you will also notice a slight de-focus of the information
when the screen decreases in size.
Eeyore" wrote in message
...


Michael Kennedy wrote:

I've had this Viewsonic PF790 19" CRT monitor for quite a few years now
and
it has been used daily since it was new without any issues. Recently I
have
noticed that large white images will cause the horizontal size to shrink
about 1cm overall. I keep my desktop set to black so if I minimize a
window
I see the picture expand or if I open a window I see the picture shrink.
It
is possible that it has always done this, but I don't believe that it
has.
Any thoughs on what might be going out?

Large white images require more current.

Clearly the supply voltage for that part of the circuitry is sagging
under the
additional current demand. A PSU problem.

Graham



Well the interesting thing is that it appears to be doing the opposite. It
is clear when a large white image is on screen, but blooms when the image is
dark.

Mike

"Jerry G." wrote in message
...
With the ageing of the monitor, the power supply regulation and scan
circuit stability has decreased. The most common cause are electrolytic
capacitors going high in ESR. If all the capacitors in the monitor were
to be checked with an ESR meter, there is a possibility of finding many
of them out of specs. This may not be a feasible repair for a monitor as
old as the one that you have.

--

Jerry G.



As old? It is from 2001 I don't really think it is that old. I have
monitors way older than that.. I have an IBM VGA monitor from 1990 and a
Tandy CGA from about 1986 that works great still.

It would be nice to get a smaller monitor on my desk, but money is an issue
so I'll be re capping the monitor when I get time.

Interesting thing is that picture color, quality, brightness is all ok.
Guess it is probably in the deflection section.

Michael Kennedy wrote:

"Jerry G." wrote:

This may not be a feasible repair for a monitor as
old as the one that you have.

snip

As old? It is from 2001 I don't really think it is that old. I have
monitors way older than that.. I have an IBM VGA monitor from 1990 and a
Tandy CGA from about 1986 that works great still.

It would be nice to get a smaller monitor on my desk, but money is an issue
so I'll be re capping the monitor when I get time.

snip

Indeed, it 'floors' me each time I read this sort of time-perception in posts;
soon we will all have concepts of longevity appropriate for fruit-flies.

Anyway, one of our local universities recently put out hundreds of late-model
monitors in hallways for giveaway since they had converted to lcd to save
power campus-wide. Are you in an area with electronics recycling? Surely
back alleys also are good sources for discarded monitors. I find good
working ones nearly every day here in a smaller U.S. city, in all screen
sizes ;-).

Regards,

Michael

"Jerry G." writes:

With the ageing of the monitor, the power supply regulation and scan
circuit stability has decreased. The most common cause are electrolytic
capacitors going high in ESR. If all the capacitors in the monitor were
to be checked with an ESR meter, there is a possibility of finding many
of them out of specs. This may not be a feasible repair for a monitor as
old as the one that you have.

While I won't claim to have anywhere near the experience that you have,
what I have seen suggests that in many cases, it may infact be a single
bad cap with high ESR that is the problem, especially if the monitor or
TV had no obvious symptoms before.

--- sam | Sci.Electronics.Repair FAQ: 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 Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

my guess would be electrolytic caps,bad ESR.
You MUST use low-ESR,105degF caps for replacements.


Well it depends on the part of the circuit the parts are in. Nothing in a
monitor gets over 85C, but 105C caps will usually last longer. There's
little reason not to buy them, but you can use what you have on hand and it
will work in most cases.


Not a task I'd suggest for a neophyte,I suggest buying a new LCD monitor.




Agreed on the first part, but the LCD monitor depends on whether he likes
them, I much prefer the image on a good CRT and know plenty of others like
me.

Well it's not my first time working on a CRT, but I just don't have tons
of expirence. I've fixed minor things in TV's before, cold solder joints,
etc. I have an ESR meter so with a little time I should be able to find
the suspect caps.




Look around the horizontal deflection and HV areas, really with an ESR meter
it's pretty easy to test almost all of the lytics in the monitor, hardest
part is getting to them, but the Viewsonics are not too bad to work on.

As old? It is from 2001 I don't really think it is that old. I have
monitors way older than that.. I have an IBM VGA monitor from 1990 and a
Tandy CGA from about 1986 that works great still.

It would be nice to get a smaller monitor on my desk, but money is an
issue so I'll be re capping the monitor when I get time.

Interesting thing is that picture color, quality, brightness is all ok.
Guess it is probably in the deflection section.



I replaced a pile of caps in a 14 year old 17" monitor a couple weeks ago,
the image looks better now than it has in years. It's old tech, but my mom
is still happy with it so I figured why replace it?

msg wrote:
Michael Kennedy wrote:

"Jerry G." wrote:

This may not be a feasible repair for a monitor as
old as the one that you have.

snip

As old? It is from 2001 I don't really think it is that old. I have
monitors way older than that.. I have an IBM VGA monitor from 1990 and
a Tandy CGA from about 1986 that works great still.

It would be nice to get a smaller monitor on my desk, but money is an
issue so I'll be re capping the monitor when I get time.

snip

Indeed, it 'floors' me each time I read this sort of time-perception in
posts;
soon we will all have concepts of longevity appropriate for fruit-flies.

Anyway, one of our local universities recently put out hundreds of
late-model
monitors in hallways for giveaway since they had converted to lcd to save
power campus-wide. Are you in an area with electronics recycling? Surely
back alleys also are good sources for discarded monitors. I find good
working ones nearly every day here in a smaller U.S. city, in all screen
sizes ;-).

Absolutely agreed. Craigslist and Freecycle (google either one) list
free, working monitors every single day. Thrift stores will hardly
accept them...although they usually have a few for $25 or less. I put
out a working 17" on the curb the other day, just because I have so many
that I'm tripping over them. I finally had to toss it....

That said, I've got a 15" Sony composite sitting next to my desk as a
'repeater' for the home theater setup (hooked to a 'Video Sender' rf
receiver). It must be 20 years old, but works great.

jak

Regards,

Michael

msg wrote:
Indeed, it 'floors' me each time I read this sort of time-perception in posts;
soon we will all have concepts of longevity appropriate for fruit-flies.

Which reminds me that time flies like an arrow, but fruit flies like a banana.

--
Dec. 6 (Bloomberg) -- Government officials and activists flying to Bali,
Indonesia, for the United Nations meeting on climate change will cause
as much pollution as 20,000 cars in a year.

On Dec 16, 9:35 am, "Michael Kennedy"
wrote:
I've had this Viewsonic PF790 19" CRT monitor for quite a few years now and
it has been used daily since it was new without any issues. Recently I have
noticed that large white images will cause the horizontal size to shrink
about 1cm overall.

start with the simplest: by changing the caps on the b+ line from the
power supply to the horizontal/line stage.. typically rated 160 volts
or more. don't bother measuring them, just replace. if no joy, then
work back into the primary of the power supply.

chances are this monitor has a few years of life left in it , so
don't give up and buy one of those 'orrid LCD things.

let us know how it goes.
-B.

"b" wrote in message
...
On Dec 16, 9:35 am, "Michael Kennedy"
wrote:
I've had this Viewsonic PF790 19" CRT monitor for quite a few years now
and
it has been used daily since it was new without any issues. Recently I
have
noticed that large white images will cause the horizontal size to shrink
about 1cm overall.

start with the simplest: by changing the caps on the b+ line from the
power supply to the horizontal/line stage.. typically rated 160 volts
or more. don't bother measuring them, just replace. if no joy, then
work back into the primary of the power supply.

chances are this monitor has a few years of life left in it , so
don't give up and buy one of those 'orrid LCD things.

let us know how it goes.
-B.

Well I thought it was thermally sensitive since it worked fine until the
monitor heated up... Now it appears to work fine for the time being. I'm
sure that I will have to fix it at some point, but right now it is not
showing any symptoms. I guess I'll have to wait for it to act up again.

Mike