Need some advice for VGA CRT

Atohmdiy

n00b
Joined
May 12, 2021
Messages
3
Hello,
I recently bought a iiyama vision master pro 454 for 25€, mostly to play some retro games. The monitor is in excellent shape and is working, but the image is very dark in some games. I had to push brightness and contrast at 100, and gamma correction at 50 to get an image that is watchable. Also the image become a little blurry when the brightness is pushed. This monitor have three mode, text picture and movies. Movies is the brightest one but the most blurry, text is very sharp but very dark.
I don't think the problem come from the DAC i am using, i tried two, one i am sure is able to do full rgb. Also try it directly connected to radeon r5 230 with a vga out, and image is even darker.
Not all games are dark, it seems related to the scene. Also when i receive the monitor it emit an unpleasant smell of burn after heat up. Now the smell is still here but less present, i was thinking that as the monitor wasn't used the last years, some dust is responsible from the smell.

Some photo to show the problem, compare to my LCD.

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I open up the monitor to see if i don't see some problems with leaking caps. Don't see any, maybe one cap is slightly rounded but it could be nothing. Any idea ?
 

spacediver

2[H]4U
Joined
Mar 14, 2013
Messages
2,658
Is your black level really deep? If so, the G2 voltage may be very low (which also would crush the image). But in my experience, G2 tends to drift up (though only have experience with trinitrons)

You may be able to adjust the g2 voltage (looks like you might need to raise it). Look up service manual and factory mode online. Haven't watched this, but may be some useful info here:

 

Atohmdiy

n00b
Joined
May 12, 2021
Messages
3
Is your black level really deep? If so, the G2 voltage may be very low (which also would crush the image). But in my experience, G2 tends to drift up (though only have experience with trinitrons)

You may be able to adjust the g2 voltage (looks like you might need to raise it). Look up service manual and factory mode online. Haven't watched this, but may be some useful info here:


Hello,
Thank you for this. Today i had some time to spend trying to fix the problem. The least i can say is that the service manual for this thing is a mess.
At first i did a mistake, as the position of this pot is not explicitly explained, i turned a knob label "ABJ" in the bottom of the two focus knob. It didn't do anything so i put it again in it's middle position as it was. Then i realize the brightness knob was deeper inside. I set brightness and contrast to 50%, gamma correction to 0, and i turn the pot. It did good, i manage to get a correct brightness.
However the image is still not sharp at it should, text for example show a light glow facing left. I tried to adjust the two focus knob to get something sharper, it's a little better but the glow and problem of sharpness is still here, also the image is sometimes "moving" (slightly narrower then bigger in ~1 sec). The border of the screen is also blurry, more than the middle.
I didn't try to play with the factory mode yet, there should be more option i guess.
 

spacediver

2[H]4U
Joined
Mar 14, 2013
Messages
2,658
sounds like you've made some progress.

Make sure your vga cable has a solid connection between video card and monitor - sometimes faulty or loose vga cables can cause strange artifacts, including the glow to the side.
 

GiGaBiTe

[H]ard|Gawd
Joined
Apr 26, 2013
Messages
1,704
If the image is dark, I'd suspect a worn out tube. CRTs are consumable items and only have a usable lifespan of several thousand hours. Assuming no other failures happen first, the tube usually goes dark as the heater and cathode guns run out of free electrons from the sacrificial metal. The color will also drift over time because the three color guns don't age at the same rate. Some of the higher end monitors have complex firmware to adjust for color drift over time so they'll maintain a decent white balance, while others will color drift. Many of my old tired CRTs went blue or purple before I recycled them.

The text smearing could be caused by many things, including a worn out tube that's being over driven. Another suspect is a crap VGA cable, manufacturers stopped making good shielded VGA cables in the late 90s. Yet other suspects are component failures on the internal analog board, which are common from being exposed to a smoking hot vacuum tube for years.
 

Atohmdiy

n00b
Joined
May 12, 2021
Messages
3
Hello,
I think i will be able to correct the glow with some convergence adjustment. I manage to enter the factory mode and there is more option for convergence, i play a little and it seems to be the solution. But i don't think this is the worst problem. After i increase the brightness, i move the crt back to my room and when i power it again, the image starts zooming in and out pretty hard, i am talking of something like 1/4 of the screen, then it stabilize. The image became also darker. Now the image is slightly zooming in and out, i made a video to show it : Also if i increase the brightness pot a little, there is quickly some bar appearing in the top of the screen.
I don't think the problem come from the tube. Colors are ok, and with the proper signal the image is great. I don't think this monitor have so much running hours, the previous owner told me he didn't use it much, in fact he bought it some years ago then stop using it very fast. Bit this is a third hand, maybe the first owner run hit hard, i don't know :)
I start to think the problem come from something dying in the analog board, this could also explain the smell. The problem is to find a way to repair it, my knowledge in electronics are limited and crt are not exactly safe to repair.
 
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