Bought from the 'E' place for cheap. Reported symptom: video comes on
and fades out. Figured it was high ESR smps caps.

Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.

There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.

This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.

Reality check: any problem with the above procedure, or experience with
this particular monitor? Any suggestions as to where to go if the above
doesn't produce a dx and fix?

Thanks as always,

jak

jakdedert wrote:
Bought from the 'E' place for cheap. Reported symptom: video comes on
and fades out. Figured it was high ESR smps caps.

Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.

There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.

This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.

Reality check: any problem with the above procedure, or experience with
this particular monitor? Any suggestions as to where to go if the above
doesn't produce a dx and fix?

Thanks as always,

jak

So far, no luck. ESRd all caps on video board. All good. Bad news is
that monitor rarely straightens up anymore. I got it to display
correctly only once this evening, so no chance of trying to reproduce
symptom via freezing components. Power supply voltages appear nominal
and clean. No effect from flexing components. Reseated all cables on
the video board.....

It looks like the horizonal rows are not being addressed, as the current
display is a series of fine vertical lines of whatever color is
predominant in that area of the display. Still some strange horizontal
scrolling effects when first powered, but they only last a few
seconds...two or three horizontal bars scroll down the screen, then
disappear.


Any help here? Is this toast [beyond my ability to fix...]? My scope
(20 mHz) is not fast enough to look at the video timing....

jak

jakdedert wrote:
jakdedert wrote:
Bought from the 'E' place for cheap. Reported symptom: video comes on
and fades out. Figured it was high ESR smps caps.

Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.

There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.

This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.

Reality check: any problem with the above procedure, or experience
with this particular monitor? Any suggestions as to where to go if
the above doesn't produce a dx and fix?

Thanks as always,

jak

So far, no luck. ESRd all caps on video board. All good. Bad news is
that monitor rarely straightens up anymore. I got it to display
correctly only once this evening, so no chance of trying to reproduce
symptom via freezing components. Power supply voltages appear nominal
and clean. No effect from flexing components. Reseated all cables on
the video board.....

It looks like the horizonal rows are not being addressed, as the current
display is a series of fine vertical lines of whatever color is
predominant in that area of the display. Still some strange horizontal
scrolling effects when first powered, but they only last a few
seconds...two or three horizontal bars scroll down the screen, then
disappear.


Any help here? Is this toast [beyond my ability to fix...]? My scope
(20 mHz) is not fast enough to look at the video timing....

jak

Has this one gotten everyone as stumped as it has me?

After three days of occasional attention, the symptoms still present as
before. I occasionally see the beginnings of a legible image, with bits
of recognizable video scrolling down the screen. Usually these break
back up into a screen full of vertical lines again; but occasionally
I'll get an 'almost' image first.

Some help, even if it's just commiseration, would be appreciated. So
far, not a single reply.....

jak

jakdedert wrote in news:ipT4k.4859$3F5.2098
@bignews2.bellsouth.net:

jakdedert wrote:
jakdedert wrote:
Bought from the 'E' place for cheap. Reported symptom: video comes on
and fades out. Figured it was high ESR smps caps.

Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.

There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.

This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.

Reality check: any problem with the above procedure, or experience
with this particular monitor? Any suggestions as to where to go if
the above doesn't produce a dx and fix?

Thanks as always,

jak

So far, no luck. ESRd all caps on video board. All good. Bad news is
that monitor rarely straightens up anymore. I got it to display
correctly only once this evening, so no chance of trying to reproduce
symptom via freezing components. Power supply voltages appear nominal
and clean. No effect from flexing components. Reseated all cables on
the video board.....

It looks like the horizonal rows are not being addressed, as the current
display is a series of fine vertical lines of whatever color is
predominant in that area of the display. Still some strange horizontal
scrolling effects when first powered, but they only last a few
seconds...two or three horizontal bars scroll down the screen, then
disappear.


Any help here? Is this toast [beyond my ability to fix...]? My scope
(20 mHz) is not fast enough to look at the video timing....

jak

Has this one gotten everyone as stumped as it has me?

After three days of occasional attention, the symptoms still present as
before. I occasionally see the beginnings of a legible image, with bits
of recognizable video scrolling down the screen. Usually these break
back up into a screen full of vertical lines again; but occasionally
I'll get an 'almost' image first.

Some help, even if it's just commiseration, would be appreciated. So
far, not a single reply.....


You have my sympathy. What makes you think that the video signals should
be much higher than 20 MHz?




--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

On Jun 14, 12:42*pm, jakdedert wrote:
jakdedert wrote:
jakdedert wrote:
Bought from the 'E' place for cheap. *Reported symptom: video comes on
and fades out. *Figured it was high ESR smps caps.

Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. *Takes like two minutes to
warm up. *Shutting the monitor down for some unknown time starts the
process all over again. *Continuous viewing yields a stable image with
good resolution, brightness and linearity. *Shutting down for short
periods is not problematic.

There is only one HV (100 @ 400v) cap in the ps. *ESR is .46, which I
assume is within tolerance. *Other caps in the ps also seem fine.

This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.

Reality check: any problem with the above procedure, or experience
with this particular monitor? *Any suggestions as to where to go if
the above doesn't produce a dx and fix?

Thanks as always,

jak

So far, no luck. *ESRd all caps on video board. *All good. *Bad news is
that monitor rarely straightens up anymore. *I got it to display
correctly only once this evening, so no chance of trying to reproduce
symptom via freezing components. *Power supply voltages appear nominal
and clean. *No effect from flexing components. *Reseated all cables on
the video board.....

It looks like the horizonal rows are not being addressed, as the current
display is a series of fine vertical lines of whatever color is
predominant in that area of the display. *Still some strange horizontal
scrolling effects when first powered, but they only last a few
seconds...two or three horizontal bars scroll down the screen, then
disappear.

Any help here? *Is this toast [beyond my ability to fix...]? *My scope
(20 mHz) is not fast enough to look at the video timing....

jak

Has this one gotten everyone as stumped as it has me?

After three days of occasional attention, the symptoms still present as
before. *I occasionally see the beginnings of a legible image, with bits
of recognizable video scrolling down the screen. *Usually these break
back up into a screen full of vertical lines again; but occasionally
I'll get an 'almost' image first.

Some help, even if it's just commiseration, would be appreciated. *So
far, not a single reply.....

jak- Hide quoted text -

- Show quoted text -

With a fixed video input signal, you should be able to figure out what
signals should be present on the leads to the LCD. A giant X painted
on a board and captured with a camcorder or regular point and shoot
camera connected to the video input of the monitor whould give you a
starting point. Do you have a schematic?

hr(bob) wrote:
On Jun 14, 12:42 pm, jakdedert wrote:
jakdedert wrote:
jakdedert wrote:
Bought from the 'E' place for cheap. Reported symptom: video comes on
and fades out. Figured it was high ESR smps caps.
Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.
There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.
This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.
Reality check: any problem with the above procedure, or experience
with this particular monitor? Any suggestions as to where to go if
the above doesn't produce a dx and fix?
Thanks as always,
jak
So far, no luck. ESRd all caps on video board. All good. Bad news is
that monitor rarely straightens up anymore. I got it to display
correctly only once this evening, so no chance of trying to reproduce
symptom via freezing components. Power supply voltages appear nominal
and clean. No effect from flexing components. Reseated all cables on
the video board.....
It looks like the horizonal rows are not being addressed, as the current
display is a series of fine vertical lines of whatever color is
predominant in that area of the display. Still some strange horizontal
scrolling effects when first powered, but they only last a few
seconds...two or three horizontal bars scroll down the screen, then
disappear.
Any help here? Is this toast [beyond my ability to fix...]? My scope
(20 mHz) is not fast enough to look at the video timing....
jak
Has this one gotten everyone as stumped as it has me?

After three days of occasional attention, the symptoms still present as
before. I occasionally see the beginnings of a legible image, with bits
of recognizable video scrolling down the screen. Usually these break
back up into a screen full of vertical lines again; but occasionally
I'll get an 'almost' image first.

Some help, even if it's just commiseration, would be appreciated. So
far, not a single reply.....

jak- Hide quoted text -

- Show quoted text -

With a fixed video input signal, you should be able to figure out what
signals should be present on the leads to the LCD. A giant X painted
on a board and captured with a camcorder or regular point and shoot
camera connected to the video input of the monitor whould give you a
starting point. Do you have a schematic?

That's an interesting concept. No, I don't have a schematic; but pulled
up another Sharp lcd service manual on the web hoping it was similar.

No such luck, but some of the diagnostic procedures spec'd a higher
bandwidth scope than mine...which I use mostly for audio bench work.

Thanks,

jak

On Thu, 12 Jun 2008 12:04:02 -0500, jakdedert
put finger to keyboard and composed:

Bought from the 'E' place for cheap. Reported symptom: video comes on
and fades out. Figured it was high ESR smps caps.

Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.

There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.

This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.

Reality check: any problem with the above procedure, or experience with
this particular monitor? Any suggestions as to where to go if the above
doesn't produce a dx and fix?

Thanks as always,

jak

FWIW, that monitor came with a 3-year warranty.

If that is not an option, then I'd be hooking up your scope to the
horizontal and vertical sync inputs and following them through. It may
help if you told us which chips are used, eg Genesis Microchip.

Have you considered that the video source may be just outside the LCD
monitor's range? I sometimes find that a 75Hz refresh rate is right at
the limit before the monitor blacks out. Try a safe 60Hz refresh rate.

What about the OSD? Is it stable? Pull the RGB cable and watch the "No
Signal" OSD window, or whatever your monitor reports.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:
On Thu, 12 Jun 2008 12:04:02 -0500, jakdedert
put finger to keyboard and composed:

Bought from the 'E' place for cheap. Reported symptom: video comes on
and fades out. Figured it was high ESR smps caps.

Actual symptom: backlight comes on, image consist of random horizontal
lines, which eventually--after some intermittent vertical
scrolling--settle into a very nice image. Takes like two minutes to
warm up. Shutting the monitor down for some unknown time starts the
process all over again. Continuous viewing yields a stable image with
good resolution, brightness and linearity. Shutting down for short
periods is not problematic.

There is only one HV (100 @ 400v) cap in the ps. ESR is .46, which I
assume is within tolerance. Other caps in the ps also seem fine.

This presents so like a classic cap issue (needs to warm up), that I'm
going to next pull the video board and check caps there...possibly get
some freeze spray and see if I can duplicate symptoms that way.

Reality check: any problem with the above procedure, or experience with
this particular monitor? Any suggestions as to where to go if the above
doesn't produce a dx and fix?

Thanks as always,

jak

FWIW, that monitor came with a 3-year warranty.

If that is not an option, then I'd be hooking up your scope to the
horizontal and vertical sync inputs and following them through. It may
help if you told us which chips are used, eg Genesis Microchip.

Have you considered that the video source may be just outside the LCD
monitor's range? I sometimes find that a 75Hz refresh rate is right at
the limit before the monitor blacks out. Try a safe 60Hz refresh rate.

What about the OSD? Is it stable? Pull the RGB cable and watch the "No
Signal" OSD window, or whatever your monitor reports.

- Franc Zabkar

Thanks Frank, for your attention.

It contains a (socketed) Winbond W78E56P-40. I pulled up the data sheet
for that, but it's beyond my experience to decipher how this generic
processor is employed in the circuit. The other large scale (100 or so
leads) chip has a logo that looks like a backward capital 'N' with
numbers MST9111. Google drew a blank on that one.

Changing video resolution makes no difference (refresh was initially 60
Hz anyway). The OSD, when accessed while 'in symptoms', is just a blue
smear up the entire height of the display. Any video input to the
display is likewise; all columns and no rows. Each column of pixels is
uniform in color from top to bottom, although that color changes with
the video content. Occasionally horizontal bands will appear, either a
lighter or darker shade...sometimes only a pixel wide, other times wider.

(I wonder if I could record and post a short video somewhere?)

For the last day or so, I've not been able to get any sort of legible
display. I hooked it up to a spare computer, on screensaver, next to my
desk, hoping to catch it actually working...turn it on occasionally for
short periods.

You might be able to tell that I'm not too familiar with the innards of
lcd displays g. This board appears to have several layers, making
visual tracing of the circuitry difficult, although I should be able to
trace continuity from the input pins to the various sm devices.

I'm afraid I'll be almost totally occupied with other business for the
rest of the week; but I'll eagerly check back here for any insight into
this....

Thanks again,

jak

On Tue, 17 Jun 2008 00:38:41 -0500, jakdedert
put finger to keyboard and composed:

It contains a (socketed) Winbond W78E56P-40. I pulled up the data sheet
for that, but it's beyond my experience to decipher how this generic
processor is employed in the circuit.

That's the microcontroller and firmwa
http://www.datasheetarchive.com/pdf/3655561.pdf

The other large scale (100 or so
leads) chip has a logo that looks like a backward capital 'N' with
numbers MST9111. Google drew a blank on that one.

It's a single-chip LCD Controller for SXGA LCD Monitors by MStar
Semiconductor:
http://www.sacg.com.tw/sacweb/marcom...Fs-new/MST.pdf

The PDF contains a functional block diagram of the chip but no
details. :-(

There are no datasheets on the MStar web site, either, only an email
address:
http://www.mstarsemi.com/products/

FWIW, the MST chip appears to be the one that interfaces to your DB-15
connector. The OSD appears to be generated within it as well. I'd be
looking around there. Maybe check its supply rails, caps, crystal?

I'm not sure what would happen if the host microcontroller (Winbond)
were to fail. If the monitor still responds to the front controls,
then I would think that the Winbond chip is working, or at least not
totally brain dead. I wonder if you would still get anything on your
screen (eg an error OSD) if you were to remove the Winbond chip. Might
be worth trying ...

Changing video resolution makes no difference (refresh was initially 60
Hz anyway). The OSD, when accessed while 'in symptoms', is just a blue
smear up the entire height of the display.

I would compare the OSD in the presence of H&V sync input with the OSD
in the absence of an input. In the latter case the MStar chip would
have to rely solely on the crystal for its reference, whereas in the
former case it would be generating a pixel clock by using its internal
PLL to multiply the H sync frequency.

Any video input to the
display is likewise; all columns and no rows. Each column of pixels is
uniform in color from top to bottom, although that color changes with
the video content. Occasionally horizontal bands will appear, either a
lighter or darker shade...sometimes only a pixel wide, other times wider.

(I wonder if I could record and post a short video somewhere?)

Youtube?

For the last day or so, I've not been able to get any sort of legible
display. I hooked it up to a spare computer, on screensaver, next to my
desk, hoping to catch it actually working...turn it on occasionally for
short periods.

You might be able to tell that I'm not too familiar with the innards of
lcd displays g.

Ditto. Maybe we can both learn something. :-)

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:
On Tue, 17 Jun 2008 00:38:41 -0500, jakdedert
put finger to keyboard and composed:

It contains a (socketed) Winbond W78E56P-40. I pulled up the data sheet
for that, but it's beyond my experience to decipher how this generic
processor is employed in the circuit.

That's the microcontroller and firmwa
http://www.datasheetarchive.com/pdf/3655561.pdf

The other large scale (100 or so
leads) chip has a logo that looks like a backward capital 'N' with
numbers MST9111. Google drew a blank on that one.

It's a single-chip LCD Controller for SXGA LCD Monitors by MStar
Semiconductor:
http://www.sacg.com.tw/sacweb/marcom...Fs-new/MST.pdf

The PDF contains a functional block diagram of the chip but no
details. :-(

There are no datasheets on the MStar web site, either, only an email
address:
http://www.mstarsemi.com/products/

FWIW, the MST chip appears to be the one that interfaces to your DB-15
connector. The OSD appears to be generated within it as well. I'd be
looking around there. Maybe check its supply rails, caps, crystal?

I'm not sure what would happen if the host microcontroller (Winbond)
were to fail. If the monitor still responds to the front controls,
then I would think that the Winbond chip is working, or at least not
totally brain dead. I wonder if you would still get anything on your
screen (eg an error OSD) if you were to remove the Winbond chip. Might
be worth trying ...

Changing video resolution makes no difference (refresh was initially 60
Hz anyway). The OSD, when accessed while 'in symptoms', is just a blue
smear up the entire height of the display.

I would compare the OSD in the presence of H&V sync input with the OSD
in the absence of an input. In the latter case the MStar chip would
have to rely solely on the crystal for its reference, whereas in the
former case it would be generating a pixel clock by using its internal
PLL to multiply the H sync frequency.

Any video input to the
display is likewise; all columns and no rows. Each column of pixels is
uniform in color from top to bottom, although that color changes with
the video content. Occasionally horizontal bands will appear, either a
lighter or darker shade...sometimes only a pixel wide, other times wider.

(I wonder if I could record and post a short video somewhere?)

Youtube?

For the last day or so, I've not been able to get any sort of legible
display. I hooked it up to a spare computer, on screensaver, next to my
desk, hoping to catch it actually working...turn it on occasionally for
short periods.

You might be able to tell that I'm not too familiar with the innards of
lcd displays g.

Ditto. Maybe we can both learn something. :-)

- Franc Zabkar

Thanks again, Frank. As detailed, I've no time for bench work this
week, but will mull over the above while mapping out my next steps.
Thinking it over, it seems obvious that the lcd is getting no horizontal
information. I need to study how that's normally supplied to an lcd
monitor, then look to where it may have disappeared. Unfortunately
there's little generic lcd troubleshooting information on the web. It
seems like usually the power supply fails. Most lcd info I've accessed
is either pretty dense engineering data...or specific fixes for various
models, which usually involves replacing one or more caps in the smps.

In fact, I've repaired a couple myself with that very problem. I was
hoping this would be one....

Perhaps we'll write that chapter in the repairfaqs. ;-) OTOH, I have
little interest in pioneering...mostly want to get my monitor working so
that I can send one off to college with my daughter.

jak