CRT Focus Adjustment

[r-486]

I opened the cover to a SyncMaster DF997. I found the two potentiometers to adjust the focus. I was definitely able to get a way better focus than what it had. Now my question is how should I go about in finding the best focus possible? I was thinking about using a high res picture with lines. Any program or something else to determine it? Highest resolution is 2048×1536.

 

[Acer_Sheep]

I don't think there is something like that, well turn on it something you think it's not well displayed and play with the controls (be aware, 25k voltage inside(just in case you might not know)

 

[r-486]

I just finished it. I'm extreme myopic (-12) so I just looked real close at the screen while adjusting and could see each pixel. I think I got it just about perfect.

 

[Surly73]

If you've got an x86 OS available, I used to use Nokia_Test for that sort of thing.

 

[Acer_Sheep]

I just finished it. I'm extreme myopic (-12) so I just looked real close at the screen while adjusting and could see each pixel. I think I got it just about perfect.

When you have such a big fraction difference, wouldn't be better for you to have larger LCD screen? Where you could set things to be much larger, using 2048 res on a CRT has to be annoying in general.

 

[r-486]

When you have such a big fraction difference, wouldn't be better for you to have larger LCD screen? Where you could set things to be much larger, using 2048 res on a CRT has to be annoying in general.

What do you mean by big fraction difference? I wanted to get an LCD that's widescreen but I don't have much horizontal space where the monitor sits. Why would 2048 be annoying? It's more pixels than 1920x1080 and lots of horizontal space is wasted on websites anyway. I could use 1600x1200 on it but I prefer higher.

 

[Surly73]

When you have such a big fraction difference, wouldn't be better for you to have larger LCD screen? Where you could set things to be much larger, using 2048 res on a CRT has to be annoying in general.

Not that it's quite on topic, but as the refractive index of corrective lenses increases, so does the chromatic abberation. This means that if you aren't looking through the exact focal center of the lenses they will start acting like prisms and make your monitor look out of convergence. I'm nowhere near -12 (more like -6 and -3 IIRC) and when I switched to high index this drove me nuts. It started changing my habit to look around the screen with my whole head instead of just moving my eyes. Bigger is not necessarily better.

This is just another one of those things that a lot of people don't know until you live it.

 

[Acer_Sheep]

Probably you are right, I have -2 astigmatism and I don't see this effect

 

[Surly73]

Probably you are right, I have -2 astigmatism and I don't see this effect

It's more the index of the plastic than the actual prescription. My -6/-3 prescription in "normal" index plastic didn't do this, but in high index plastic the same prescription displayed it very clearly. The strength of prescription could make it even worse, I suppose. I only have the one pair of eyes to play with personally

http://en.wikipedia.org/wiki/Lens_%28optics%29#Aberrations

 

[IndianScout]

on the back of the chasis on the flyback transformer will be a focus adjustment also I think it's the top one the bottom one should be high voltage adj.

 

[r-486]

I'm using 1.57 mid-index lenses. I don't have a problem with chromatic aberration or I'm just so used to it to not notice it. It's not my vision that was the problem. The CRT was really out of focus from moving around a lot. A bump and time probably whacked it out of focus.

on the back of the chasis on the flyback transformer will be a focus adjustment also I think it's the top one the bottom one should be high voltage adj.

It was towards the back on the left side. By left I mean when facing the CRT's front. There were actually two focus pots.

 

[Surly73]

I'm using 1.57 mid-index lenses. I don't have a problem with chromatic aberration or I'm just so used to it to not notice it. It's not my vision that was the problem. The CRT was really out of focus from moving around a lot. A bump and time probably whacked it out of focus.



It was towards the back on the left side. By left I mean when facing the CRT's front. There were actually two focus pots.

Yep. Some CRTs have two focus pots, some have one focus and one HV trim. Look for silkscreening or raised lettering on the parts before twiddling. if you can't see any labeling, do your initial twiddles with a precise memory of the initial position in case you need to return the adjustment to that point.