VOGONS


CRT and wrong colours

Topic actions

Reply 20 of 37, by pentiumspeed

User metadata
Rank l33t
Rank
l33t

When I see this I knew CRT had degraded some, re-adjust the color knobs on the CRT board if has one. Another issue is capacitors in the video path especially on the CRT board that plugs into CRT's end.

Cheers,

Great Northern aka Canada.

Reply 21 of 37, by DoZator

User metadata
Rank Newbie
Rank
Newbie

For me, like (Seeing the first screenshot), the picture on the CRT looks somehow more natural and deeper (Except for color problems). I had the same problem on a Diamondtron based Iiyama. Also with too much green. I solved the problem only by entering the engineering menu and setting the colors there so that it would be comfortable. There you can either increase or decrease any color individually. I think for your monitor, an engineering menu should also be provided, with advanced settings.

Reply 22 of 37, by rasz_pl

User metadata
Rank Oldbie
Rank
Oldbie
Boohyaka wrote on 2022-07-20, 14:31:
I've had a Sony Trinitron with an obvious green tint, which looks pretty similar to the kind of issue you're having, and I've be […]
Show full quote

I've had a Sony Trinitron with an obvious green tint, which looks pretty similar to the kind of issue you're having, and I've been lucky to have someone point me to hardforum.com post sharing the software and tutorial to restore it to its former glory using a simple USB to TTL adapter and a software called WinDAS. Fully story there: Sony Multiscan CPD-G500 backlight/green tint issue where you will find the hardforum link if you want to read it all.

So the issue is "G2 Voltage" and I've been able to tune it down to restore the screen to perfect black. No more green bias!

Your screen definitely has a special service mode accessible through a specific connector and software as well - see page 13 of the service manual: https://www.manualslib.com/download/781240/Lg … tron-F700p.html but there's not a lot of specific information on what is needed, and I have absolutely no idea if WinDAS is specific to Sony Trinitron only or if there's hope to make it work on other brands like yours.

In any case, finding the interface and software mentioned in the service manual may be worth some effort, as section 5 "white balance and luminance" mentions controls like R-BIAS/G-BIAS/B-BIAS that sound interesting to fix your problem.
I really am not sure how relevant or useful this information may be. There are some knowledgeable peeps on that board, so maybe it is worth sending a message in a bottle in reply to the topic, or create a new one?

As a CRT lover and dedicated preservationist, I find so sad that the knowledge and tools to service CRT screens is slowly dying. Hope you manage to fix yours, good luck

this is right on the money

guy this is modern CRT, there are no knobs, and most likely no potentiometers on the pcb, its all digital.

Reply 23 of 37, by vorob

User metadata
Rank Oldbie
Rank
Oldbie

Okay, let me summ it up. I got this screen for free. Its history is a mystery, I was told it was barely used but no idea. The green tint didn’t fade away with my yesterday long use. But! With the use of RGB temperature setting in monitor menu I was able to get rid of green tint so case is solved, in some way.

I was thinking that it will be self-fixed without my need of altering colours, but no.

Later I’ll disassemble the unit and clean everything there, reattach cables, check capacitors.

For now I just happy to touch this glorious CRT technology, these deep blacks and high dynamic resolution 😀

961F60D1-003F-4410-9CEB-4B8372A86098.jpeg
Filename
961F60D1-003F-4410-9CEB-4B8372A86098.jpeg
File size
202.25 KiB
Views
422 views
File license
Public domain

Reply 24 of 37, by pentiumspeed

User metadata
Rank l33t
Rank
l33t

Perfect! Easiest way is display grey scale bars or turn down color all the way down, adjust color controls for perfect white and all the greys are not tinted colors. Once you turn up color, you will be amazed.

Cheers,

Great Northern aka Canada.

Reply 25 of 37, by rasz_pl

User metadata
Rank Oldbie
Rank
Oldbie

It might not be that simple, color temperature setting is one fixed slope, but the defect might be non linear so you tweak it to look fine in full brightness and it still shows on dark images or vice versa

Reply 26 of 37, by pentiumspeed

User metadata
Rank l33t
Rank
l33t

Actually this is what exactly what we do even still now. I had to readjust both the LCD TV and monitor so they look correct.

Doing this correctly corrects the over blown colors and looks neutral.

Cheers,

Great Northern aka Canada.

Reply 27 of 37, by vorob

User metadata
Rank Oldbie
Rank
Oldbie
2682F806-6CBB-4442-952D-94EF12D1FC1A.JPG
Filename
2682F806-6CBB-4442-952D-94EF12D1FC1A.JPG
File size
1.86 MiB
Views
355 views
File license
Public domain

Guys, i've got some news! I found service menu. No idea if these values are from factory or previous ovener, but green driver is definetly overdone. I've made RDRV and BDRV to 100 and GDRV to 80. Now i've got proper colours and default RGB menu can be used for tempereture setting, not the colour fix.

I wonder what are the default values and what other menus do, maybe i need to alter there smth... 😀

Reply 29 of 37, by pentiumspeed

User metadata
Rank l33t
Rank
l33t
vorob wrote on 2022-07-22, 12:49:

2682F806-6CBB-4442-952D-94EF12D1FC1A.JPG

Guys, i've got some news! I found service menu. No idea if these values are from factory or previous ovener, but green driver is definetly overdone. I've made RDRV and BDRV to 100 and GDRV to 80. Now i've got proper colours and default RGB menu can be used for tempereture setting, not the colour fix.

I wonder what are the default values and what other menus do, maybe i need to alter there smth... 😀

Did you do this adjustments while displaying grey scale from black through grey bars dark to nearly white and last bar is white? This is easiest way.
Reasons for this grey scale bars used for adjustment:
1. Easier to see how overdone the brightness of overall.
2. Easier to get proper look that you can see all the greys linearly, not too pale or not too dark to tending one or other end.
3. Easier to spot any tint of color showing in the grey scale especially grey bars while hard to do this with just black or white or displaying color bars.

Standard way is reset the customer user settings to defaults, always! If brightess is too high, adjust down some.
If there is no way to do grey scale, instead display color bars and through the user setting, turn down color to zero, this will show grey scale for now. Important is choose a color bars *including* white and black in it.

Every TV or monitor I got ahold of were too much in brightness and compressed color look. This was to "upsell" to buyers and especially on CRT were hard on cathodes. Done correctly, the brightness and color corrected via grey scale method you will find settings will be much less than before and extend the CRT's cathodes life significantly.

Done correctly, you should able to see every details without blown out color, greyish or too dark overall, and details easier to understand, skin tone, and especially browns look good.

Cheers,

Great Northern aka Canada.

Reply 30 of 37, by vorob

User metadata
Rank Oldbie
Rank
Oldbie

You are talking about this image?

f83d7060dcdb8882_zoom.jpg
Filename
f83d7060dcdb8882_zoom.jpg
File size
31.78 KiB
Views
300 views
File license
Public domain

I can see all segments separately, so no clipping in shadows and bright areas.

Reply 31 of 37, by CrFr

User metadata
Rank Newbie
Rank
Newbie
vorob wrote on 2022-07-22, 12:49:

Guys, i've got some news! I found service menu. No idea if these values are from factory or previous ovener, but green driver is definetly overdone. I've made RDRV and BDRV to 100 and GDRV to 80. Now i've got proper colours and default RGB menu can be used for tempereture setting, not the colour fix.

I wonder what are the default values and what other menus do, maybe i need to alter there smth... 😀

How do you access the service menu? I have the exact same monitor, and it would be interesting to have a go.

Reply 32 of 37, by vorob

User metadata
Rank Oldbie
Rank
Oldbie

Press and keep pressing select and then press power button for some time. Screen will blink and now when you open degauss menu it will open service menu instead.

Take a picture of your values please. Want to compare 😀

Anything particular you wanna check there?

Reply 33 of 37, by CrFr

User metadata
Rank Newbie
Rank
Newbie

I remembered my model wrong. It was F700B, not F700P. It looks just the same as yours, but I can't get to service menu. Power led blinks once when I try it, but nothing else seems to happen.

Problem I have with it is, picture is slightly nonlinear vertically. I mean, for example, row of text is taller at the bottom of the screen than it is at the top. I bought this monitor new in sealed box few years ago,and it works perfect except for this flaw. If anyone has ideas how to get to the menu (if there is a menu in this one), I'd gladly hear it 😀 Service manual just talks about making adjustments with cable and PC software.

Reply 34 of 37, by pentiumspeed

User metadata
Rank l33t
Rank
l33t
vorob wrote on 2022-07-23, 10:19:

You are talking about this image?

f83d7060dcdb8882_zoom.jpg

I can see all segments separately, so no clipping in shadows and bright areas.

Yes that one. This what I use all the time when setting up or maintaining tv and monitors.

Cheers,

Great Northern aka Canada.

Reply 35 of 37, by vorob

User metadata
Rank Oldbie
Rank
Oldbie

Guys, can you please clarify one thing for me. If I open a complete black image on crt, should properly set up monitor emit light of not? The reason I’m asking is because I can’t understand what I should strive for.

As I said before, I can see all bars in contrast test from Nokia.

Reply 36 of 37, by mkarcher

User metadata
Rank Oldbie
Rank
Oldbie
vorob wrote on 2022-08-05, 19:54:

Guys, can you please clarify one thing for me. If I open a complete black image on crt, should properly set up monitor emit light of not? The reason I’m asking is because I can’t understand what I should strive for.

As I said before, I can see all bars in contrast test from Nokia.

If you open a completely black image, the monitor should not emit any light (or at least be very close to it).

Reply 37 of 37, by pentiumspeed

User metadata
Rank l33t
Rank
l33t

Correct, any scanlines not visible too where any black areas.

This will be little tougher with aged CRT. Worn cathode surfaces emits less, forcing one to adjust higher to compensate, at the point you can't have black anymore and then the appearance of image look poor.

This is why I do not like Sony (All!) and any monitors and TV that based on automatic kine adjustment. Cannot be shut off and is major cause of killing CRT rapidly, no matter what.

Cheers,

Great Northern aka Canada.