SHARP 28JW-73H - - Need Help with Service Mode Adjustments

[Alasdair Campbell]

Hey there everyone,

I recently aquired a SHARP 28JW-73H 16:9 100Hz CRT TV through the wonderful
freeshare network of Glasgow, Scotland. When I got it back to my house
following a fairly benign car journey the TV would occasionally show a green
cast, other times showing a perfect picture. Cycling the power button would
normally fix this. The problem got worse, for no obvious reason until the
image was always green cast.

Anyway to cut a long story short, found the service for the Sharp GA-200
chassis, got into it's service mode to see if there was any 'return to
factory defaults' or similar option, messed around (Uh oh!) with the options
for {R,G,B} Gain & Cutoff to no avail, then read about degausing the screen
with another CRT monitor. I was dubious as I'd heard the TV degausing a few
times since the problem appeared. Tried it and it seemed to solve the green
cast - now it was blue! ;-)

Went back into the Service mode and set Gain & cut off to similar values for
both R,G & B. Cycled the power button and first thing I saw was strong blue
cast on picture, then 4 or 5 diagonal blue lines with blue cast, then good
picture; albeit flickering maybe 2 or 3 times a second.

The flicker seems to take the blacks in the image and give them a
purple/blue tint for the duration. Whites are largely unaffected.

As I'm very close to a perfect image I don't want to mess with things _too
much_ though it seems like I should investigate the Cutoff & Gain options
for the Blue emitter?

I've searched for help on what these actually mean but I'm still fairly
clueless.

Any suggestions?

Alasdair

 

[Meat Plow]

Hey there everyone,

I recently aquired a SHARP 28JW-73H 16:9 100Hz CRT TV through the wonderful
freeshare network of Glasgow, Scotland. When I got it back to my house
following a fairly benign car journey the TV would occasionally show a green
cast, other times showing a perfect picture. Cycling the power button would
normally fix this. The problem got worse, for no obvious reason until the
image was always green cast.

Anyway to cut a long story short, found the service for the Sharp GA-200
chassis, got into it's service mode to see if there was any 'return to
factory defaults' or similar option, messed around (Uh oh!) with the options
for {R,G,B} Gain & Cutoff to no avail, then read about degausing the screen
with another CRT monitor. I was dubious as I'd heard the TV degausing a few
times since the problem appeared. Tried it and it seemed to solve the green
cast - now it was blue! ;-)

Went back into the Service mode and set Gain & cut off to similar values for
both R,G & B. Cycled the power button and first thing I saw was strong blue
cast on picture, then 4 or 5 diagonal blue lines with blue cast, then good
picture; albeit flickering maybe 2 or 3 times a second.

The flicker seems to take the blacks in the image and give them a
purple/blue tint for the duration. Whites are largely unaffected.

As I'm very close to a perfect image I don't want to mess with things _too
much_ though it seems like I should investigate the Cutoff & Gain options
for the Blue emitter?

I've searched for help on what these actually mean but I'm still fairly
clueless.

Any suggestions?

Alasdair

Go here and read.

http://www.electronics-lab.com/articles/files/crt.pdf

 

[Alasdair Campbell]

Go here and read.

http://www.electronics-lab.com/articles/files/crt.pdf

Thanks for that link, I've learned more about CRT in 6 pages than I have in
20 years!

I'm not sure that things are working right with the adjustments, when in
service mode the picture comes up first a lot darker than in normal mode,
when I switch to the page that adjusts gain and cutoff the image gets much
better, though slightly too bright with poor black levels. I set R Gain to
max, reduced G & B until a good balance of colour was acheived. I notice
that the cut off for R.,G & B are all set to max! - maybe thats what caused
the flickering, so I reduce each cut off value arbitrarily. Am I right in
thinkthing that as Cut off value affects the level at which black is
displayed a higher cut of value would make the overal picture darker - as
signal levels normally displayed are 'cut-off' ? This would make sense as
when viewing the TV the picture was darker than it should have been.

I go back to normal mode and now the image has a strong Blue cast, as if the
B gain is too high. The problem with making any judgements on this is that
while adjustings these values the image is pretty good, once I go back to
normal running the image is noticeably poorer in one way or the other.

Why would the service mode display the image differently to normal running?

This is from the service manual:
"2. Follow the procedure below to set the Cut Off.
2.1 Adjust G2.
2.2 Tune a white pattern.
2.3 Adjust colour to minimum.
2.4 Position colorimeter in the centre of screen.
2.5 Adjust brightness and contrast to obtain a luminance of ~20 NITS.
2.6 Operate in Service Mode and select location RED CUT OFF, GREEN CUT OFF
and BLUE CUT OFF, to
obtain colour coordinates:
X=0.290 ± 0.015 Y=0.300 ± 0.015
To increase press volume-up button and to decrease press volume down button.
RED CUT OFF alter X coordinate.
GREEN CUT OFF alter Y coordinate.
BLUE CUT OFF alter X and Y coordinate."

From this I see I have no colorimeter, and don't know how to adjust G2 - but
supposing it was never adjusted in the first place that is no problem.
In reference to colour coordinates when in service mode there are two sets
of hexadecimal figures, like so
06 51 45 4C
06 06 06 50
presumably X and Y respectively. Or am I suppsed to read the coordinates
from the colorimeter?

Sorry for the confused queries...

Alasdair

 

[Meat Plow]

Thanks for that link, I've learned more about CRT in 6 pages than I have in
20 years!

I'm not sure that things are working right with the adjustments, when in
service mode the picture comes up first a lot darker than in normal mode,
when I switch to the page that adjusts gain and cutoff the image gets much
better, though slightly too bright with poor black levels. I set R Gain to
max, reduced G & B until a good balance of colour was acheived. I notice
that the cut off for R.,G & B are all set to max! - maybe thats what caused
the flickering, so I reduce each cut off value arbitrarily. Am I right in
thinkthing that as Cut off value affects the level at which black is
displayed a higher cut of value would make the overal picture darker - as
signal levels normally displayed are 'cut-off' ? This would make sense as
when viewing the TV the picture was darker than it should have been.

I go back to normal mode and now the image has a strong Blue cast, as if the
B gain is too high. The problem with making any judgements on this is that
while adjustings these values the image is pretty good, once I go back to
normal running the image is noticeably poorer in one way or the other.

Why would the service mode display the image differently to normal running?

This is from the service manual:
"2. Follow the procedure below to set the Cut Off.
2.1 Adjust G2.
2.2 Tune a white pattern.
2.3 Adjust colour to minimum.
2.4 Position colorimeter in the centre of screen.
2.5 Adjust brightness and contrast to obtain a luminance of ~20 NITS.
2.6 Operate in Service Mode and select location RED CUT OFF, GREEN CUT OFF
and BLUE CUT OFF, to
obtain colour coordinates:
X=0.290 ± 0.015 Y=0.300 ± 0.015
To increase press volume-up button and to decrease press volume down button.
RED CUT OFF alter X coordinate.
GREEN CUT OFF alter Y coordinate.
BLUE CUT OFF alter X and Y coordinate."

From this I see I have no colorimeter, and don't know how to adjust G2 - but
supposing it was never adjusted in the first place that is no problem.
In reference to colour coordinates when in service mode there are two sets
of hexadecimal figures, like so
06 51 45 4C
06 06 06 50
presumably X and Y respectively. Or am I suppsed to read the coordinates
from the colorimeter?

Sorry for the confused queries...

Alasdair

I answered you in another thread. May I suggest that in the future, you
not create multiple threads as this adds to the confusion. Your question
is technically specific to the brand and model of your Sharp TV and would
be better answered by someone who has had these same problems. Maybe the
adjustments are not being stored? You mentioned they should be
automatically applied. My Panasonic 51" RP needs a confirmation to write
the data. Unless you're lucky enough to find someone here that has worked
on this set and experienced the same problems and has resolved them, you
might want to contact Sharp tech support and see what they have to say.
Glad you found the link I posted useful.

 

[Alasdair Campbell]

I answered you in another thread. May I suggest that in the future, you
not create multiple threads as this adds to the confusion. Your question
is technically specific to the brand and model of your Sharp TV and would
be better answered by someone who has had these same problems. Maybe the
adjustments are not being stored? You mentioned they should be
automatically applied. My Panasonic 51" RP needs a confirmation to write
the data. Unless you're lucky enough to find someone here that has worked
on this set and experienced the same problems and has resolved them, you
might want to contact Sharp tech support and see what they have to say.
Glad you found the link I posted useful.

Yeah that link was brilliant, and I've just had a look through the rest of
the site, there's so many articles on things I'm interested in - all in one
place, thanks again.

I went into the service mode after setting the gain/cutoff levels and
pressed a combination of buttons, power cycled and the picture was as good
as it was in service mode, so a sort of success although the image isn't
perfect - see below - and I couldn't say for sure which button caused the Tv
to update the eeprom.

I'm a litle bit wary of adjusting those values again incase the eeprom trips
out again and I'm left with a really bad picture. However in the interests
of mental health I would still be keen on tweaking the values to get the
best image possible.

Other than the instructions given in the service manual I quoted in a
previous email (in this thread) are there easier ways to set the gain cutoff
accuratly with only basic tools - eg the EYES..?

Thats the sort of information I was looking for in the other thread. I was
aware that I could have confused matters by posting so soon after this
thread, but I wanted to make the distinction between the queries - that
query was me requesting more information on the calibration process, while
this post is to do with the specific Sharp eeprom problem.

I'm going to try Sharp general support line tomorrow and see if I can get
through to someone who knows about this sort of thing.

The TV is currently almost perfect except for a slight flicker. I'm sure
it's from the blue gun as it's primarily purples and blues that flicker. I
presume I need to modify the gain and or cut off values for it, but that is
where my expertise finishes.

Alasdair

 

[Meat Plow]

Yeah that link was brilliant, and I've just had a look through the rest of
the site, there's so many articles on things I'm interested in - all in one
place, thanks again.

I went into the service mode after setting the gain/cutoff levels and
pressed a combination of buttons, power cycled and the picture was as good
as it was in service mode, so a sort of success although the image isn't
perfect - see below - and I couldn't say for sure which button caused the Tv
to update the eeprom.

I'm a litle bit wary of adjusting those values again incase the eeprom trips
out again and I'm left with a really bad picture. However in the interests
of mental health I would still be keen on tweaking the values to get the
best image possible.

Other than the instructions given in the service manual I quoted in a
previous email (in this thread) are there easier ways to set the gain cutoff
accuratly with only basic tools - eg the EYES..?

Thats the sort of information I was looking for in the other thread. I was
aware that I could have confused matters by posting so soon after this
thread, but I wanted to make the distinction between the queries - that
query was me requesting more information on the calibration process, while
this post is to do with the specific Sharp eeprom problem.

I'm going to try Sharp general support line tomorrow and see if I can get
through to someone who knows about this sort of thing.

The TV is currently almost perfect except for a slight flicker. I'm sure
it's from the blue gun as it's primarily purples and blues that flicker. I
presume I need to modify the gain and or cut off values for it, but that is
where my expertise finishes.

Alasdair

I went through the entire set of service mode adjustments on my 51" Pana.
I did have the entire manual and borrowed the test gear I needed. Many of
the settings should only be done with the proper test gear. I was pleased
to discover that the factory adjustments were very close after 7 years of
use. Hope you get your set tweaked to where you are happy with it and I'm
glad I could have helped in any way.