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

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

Reply to
Alasdair Campbell
Loading thread data ...

On Sun, 07 Jan 2007 02:54:25 +0000, Alasdair Campbell Has Frothed:

Go here and read.

formatting link

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

 Click to see the full signature
Reply to
Meat Plow

_too

options

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

Reply to
Alasdair Campbell

On Sun, 07 Jan 2007 15:19:45 +0000, Alasdair Campbell Has Frothed:

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.

Reply to
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

Reply to
Alasdair Campbell

On Tue, 09 Jan 2007 01:02:47 +0000, Alasdair Campbell Has Frothed:

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.

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794
Reply to
Meat Plow

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.