Samsung SyncMaster 955DF dim image fix

[rattlesnake]

This display looks a bit dim but the image is otherwise fine. I already set the contrast to 100 and the brightness to 50 (more than that is counterproductive, it becomes hazy).

To enable extra tuning, I have to enable the "Highlight Zone" function and stretch it to full screen. That way it looks really bright/intense and really good! I wish I could set it permanently like this, but as soon as you change the display mode/resolution or you turn the monitor off, you lose the "Highlight zone" config and you have to manuallly activate it again. Also, the manual says that this function is automatically deactivated after 3 hours.

Considering that the monitor is capable of displaying with the proper intensity, could adjusting a potentiometer in the back of the chassis be a permanent fix?
I guess that a reasonable increase in intensity would do, it doesn't need to be as bright as the Highlight Zone function if that's not possible.

The story is that I recently got this monitor, plastics look close to new (it doesn't seem to have been used much) but I'm not familiar with CRTs, that's why I'm asking this (I know about the dangers of a discharge from the cathode).

I'm very attracted to CRTs because of the nature of them and the "life" they emanate, as opposed to the emotionless LEDs.

I've been reading about CRTs and watching videos. Generally there two potentiometers, one for the screen brightness and another one for the focus, what about this model? I've read that the SyncMaster 997DF has two focus pots. How many screen/intensity pots does the 955DF have? Do I have to remove the entire plastic case to regulate them? I couldn't find a maintenance manual for this monitor.

Any advice would be greatly appreciated

[momaka]

Re: Samsung SyncMaster 955DF dim image fix

If I remember correctly from when I opened my Samsung 955DF a while back, there should only be 2 knobs on the flyback: Focus and Screen (G2 adjustment.) Screen (G2) is the one to adjust for more screen brightness. And yes, you need to remove the plastic cover to gain access to those adjustment knobs / pots on the flyback. There is a metal case / shield around the back of the tube, but if I remember correctly again, there is a cutout on the left side of the metal shield (when monitor screen is facing you), so luckily you don't need to remove this metal shield.

BUT WAIT!

Before doing any of those adjustments, perform the following test:
Put an all-black image on the screen and display it full screen, so you get an entire black full screen. Do this in a completely dark room (i.e. at night with lights off) and after the monitor has warmed up for about 30-40 minutes. Now look at the screen and evaluate the screen brightness - if you can see the black screen "glowing" in the dark, then you probably should NOT adjust the G2 / screen knob. Instead, the issue might be signal-coupling electrolytic caps bad caps on the video board (the board attached to the back of the tube neck.) However, if the black screen looks trully invisible in your dark room, then you might have to bump up the G2. To adjust the G2 properly, set the screen brightness to about 50% and adjust G2 up so that you can just about start to see a very faint glow of the black image on the screen.

In the case of my Syncmaster 955df, my G2 was set so high from the factory, that even with brightness = 0% and contrast = 50-60%, I still get a very "washed out" black image on my screen with the above test. I was going to adjust it at one point, but never did as it turned out to be a good thing to have the screen brightness slightly higher for gaming in modern e-sport titles that sometimes have poor contrast in dark areas. Otherwise, for a better "cinematic" experience / image, set G2 as stated above. Deep black colors are nice for movies and cinematic games... but may need a bit of correcting with a gamma curve (in software) so that the image doesn't look too dark - at least IME / IMO.

Hope this helps and let us know how it goes.

[rattlesnake]

Re: Samsung SyncMaster 955DF dim image fix

Hey momaka! How are you, legend? I read on an old topic that you had this monitor and was hoping that you could help.

I finally disassembled it, took many precautions, including pushing down the power button for several seconds and discharging the anode with a screwdriver + cable and an alligator clip to the chassis. It didn't make any noises or sparks at all. I repeated the process many times with a hand behind my back. Nothing. I discovered that the tip of the screwdriver had some sort of grease that comes from suction cup or around it.

There was no cutout on the left side, so I had to remove the metal shielding, just 3 screws and then pull gently.

Then I found the flyback. There are two focus potentiometers but to my dismay there is no "screen" potentiometer. Take a look:



I thought that it was a just a plastic cover with a pot underneath but it's not the case. It's hard plastic, all one piece with the transformer. Like some bad joke =(

I didn't touch the focus pots.

A little further on the PCB there's a potentiometer labelled VR401. It only moves the screen on the X axis. I reverted it to its original position more or less. Is there any way to be sure? According to the maintenance manual that's the back raster pot.



I found a reference to G2 in the back, but there's no potentiometer there either.

BUT WAIT!

Before doing any of those adjustments, perform the following test:

So I did your test with 50% contrast and 0% brightness, with Highlight Zone deactivated.
Full screen black image with irfanview. With lights on the monitor glow is imperceptible. With all lights off you can perceive a very dim glow. If I enable the 'Highlight Zone' mode, then the glow is more intense.
So... what's the veredict?
I still want to crank up the G2 but there's none...

Would you advice to change the caps on the video board?

The capacitors look fine but they could have dried up... recapping the board wasn't in my plans but... if you are absolutely sure that that's the answer... I'll do it! I'm afraid of destroying the tube, so I'll accept all your advice on how to remove the video board properly. I'll look for other sources of info too. CRT repairing info is not so easy to come by...

Before reading your answer I had already disassembled it, and since I didn't find the screen pot, I started thinking to myself,
"Is there a way to hack the logic part of the board so that it always uses this Highlight Zone mode?".

Then reading the "confidential" maintenance manual (here it is, by the way) I was puzzled by so many mentions to functions/options that don't exist and the word "softjig" comes up a lot. Looking it up, I discovered that you can program the monitor's (EEPROM?) settings using the I2C bus.
The only source of info and software that I found is in Russian and it's going to be tricky to get everything right, but I think that I already have figured out most of it.
I'm going to try model 2, this one:



The only IC I'd need is a 74LS05 and assuming I put it together correctly, then I'd have to find out how to adjust the picture intensity (luminance?) with the software.

Hope this helps and let us know how it goes.

Bonus info and pictures:

The board model is AN19LJ/CA19JS/PU19JV
it also says
CODE NO: BH41-00224A

it has two distinct ICs:

*AN19J 116
(FCFO) 31.03.04

* SAMSUNG N407
S1D2519X01-A0
IW270B

Tube info:
TYPE M46QCK761X214
K-[M/T4/DFX] [SCD]
F01 K 31201316

According to a sticker on a heatsink:
CDT = SSD
TYPE = IFT
FBT = SEMCO
INCH = 19








The adapter I'll make:

[momaka]

Re: Samsung SyncMaster 955DF dim image fix

Hey momaka! How are you, legend? I read on an old topic that you had this monitor and was hoping that you could help.

Hey there!
Sorry about not replying for quite a while. For some reason, I thought I had replied to your last reply above, until I realized it was all in my head and I never did.

Yes, I still have and use my 955DF CRT monitor (almost daily up until mid May of this year, but been busy with a few life changes recently.)

I finally disassembled it, took many precautions, including pushing down the power button for several seconds and discharging the anode with a screwdriver + cable and an alligator clip to the chassis. It didn't make any noises or sparks at all. I repeated the process many times with a hand behind my back. Nothing. I discovered that the tip of the screwdriver had some sort of grease that comes from suction cup or around it.

Yes, that grease is there to help create better seal between the high-voltage (HV) anode on the inside of the CRT and the HV tap on the flyback.
I usually don't touch under there unless I need to remove the main board / flyback transformer. Most modern monitors also tend to discharge the HV anode within a few minutes of turning Off (that static sound you hear when the monitor turns off.)

Actually, the one item to beware more of, if you ever try to service the mainboard of any CRT monitor, is to make sure the filter caps for the +B line and DC input (from the AC line) are discharged. Those are the ones that might not be discharged and give you an unpleasant shock.

Then I found the flyback. There are two focus potentiometers but to my dismay there is no "screen" potentiometer
....

I found a reference to G2 in the back, but there's no potentiometer there either.
...
Then reading the "confidential" maintenance manual (here it is, by the way) I was puzzled by so many mentions to functions/options that don't exist and the word "softjig" comes up a lot. Looking it up, I discovered that you can program the monitor's (EEPROM?) settings using the I2C bus.

Oh wow, you're 100% right here and it looks like I have completely forgotten about this over time. Indeed way back when I was looking up the same information as you - how to tweak the G2 (in my case, I wanted to lower it, because even at 0% brightness, I still find the monitor has too much back glow / brightness) - I ran into the same "issue" relating to the SoftJig tool... so I just gave up and continued to use the monitor as-is.

But you're correct, if you want to adjust G2, you have to use SoftJig interface. I imagine this is similar to WinDAS for Sony CRT monitors, which is also something I've never used but read a good deal about (in connection, again, with lowering the G2, as that seems to be quite the common problem on certain and/or more modern Sony CRT monitors.)

The only IC I'd need is a 74LS05 and assuming I put it together correctly, then I'd have to find out how to adjust the picture intensity (luminance?) with the software.

Sounds like you're on the right track.
I personally never got this far... but will follow this thread and still chime in if there is anything to add.
Let me know if you need any help reading / figuring out anything through that Russian link. I don't know Russian... but I know enough cyrillic to sometimes understand / figure out fundamental things. Google Translate is really helpful these days... but sometimes it can't get everything 100% either.

So I did your test with 50% contrast and 0% brightness, with Highlight Zone deactivated.
Full screen black image with irfanview. With lights on the monitor glow is imperceptible. With all lights off you can perceive a very dim glow. If I enable the 'Highlight Zone' mode, then the glow is more intense.
So... what's the veredict?

Well, I can never say with 100% confidence without being able to see the monitor in person... but going by this description, it sounds like the G2 on your monitor might be OK, if not slightly high too, like on my 955DF.

A properly-calibrated monitor should show ZERO glow on a full black screen in a completely dark room when the brightness control is set to 0%. Most monitors will go completely dark even way before this, typically in the 10-20% range.

So I think the G2 is likely OK on your monitor.
Dim colors could be caused by failing signal caps on the CRT neck board. But before we jump to any conclusions, have you tried viewing / using your CRT in a completely dark room? The way I run my 955DF is with the brightness set to 0% and contrast set anywhere from 65% (when I'm reading at night and want a more "mellow" / easy picture for my eyes) to 90% (when I want very bright and popping colors.) With that said, I stopped trying to use my 955DF during the day almost from day 1 when I got it. I find that the flat-screen geometry on this monitor is really good at trapping external light and makes the colors really poor. The anti-reflective coating doesn't seem to help much. Thus, try viewing your monitor with the brightness and contrast settings above in a dark room and see if you like it then. If the pictures still looks too washed out, then there might indeed be an issue with the monitor. But if not, it might be just wrong expectations. I suspect a lot of people have forgotten downs of having to use a CRT monitor in a bright room. Sure some CRTs were better than others... but as far back as I can remember using my CRT monitors (since early 2000's), I never liked how they looked in a bright / normally-lit room. I always put my blinds down and either dimmed or completely turned off the lights to get good contrast on the screen.

If you can, try snapping a picture of your screen in a completely dark room. Don't use the Highlight Zone. Just regular image on the screen with the settings above. Maybe that will tell us more.

As far as technicals go, I looked into the service / maintenance manual of this monitor, and it appears the RGB signal is first fed through an amplifier on the neck board that's responsible for the "Highlight Zone", and then the signal is fed into another pre-amp for proper RGB amplification. Between those stages, there are some electrolytic coupling caps that could have started to get leaky (electrically) and thus perhaps that might be the reason for the "weak" colors.

In any case, try snapping some pictures of the "washed out" colors and another with the settings and dark room mentioned above. Hopefully that can help reveal if there is an issue with the image.