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14" Packard Bell CRT Brightness and Alignment Issues

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First post, by anetanel

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I got a 14" Packard Bell CRT from 1993 ( can be seen in the youtube video in the bottom)
It works pretty well on DOS and in windows in resolution of up to 640x480, but when trying to use it in 800x600, the brightness decreases significantly, and the picture needs to be significantly re-aligned to be in the center.
I have it open since I just retrobrighted the plastics, and I poked around with the various pots. I can make the picture bright and centered in either 640x480 OR 800x600, but not in both.
My assumption is that some capacitors are not working as well as they should, and the changes in voltage that comes with changing the resolutions manifest in those issues.
Is it a fair assumption, or did old VGA monitors were good only for some resolutions?

https://www.youtube.com/watch?v=TXm4KsqZDn0

Reply 1 of 3, by Jo22

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I'm speaking under correction here, so please don't take that at face value, but..
These old monitors, - I once had a similar one by IBM (PS/2 line) -, are not multisync but rather single-frequency.

That means, they are aligned for a single frequency. If you prefer running in 800x600, you can do that, but have to re-adjust manually each time you change resolution.
Or use an oddball frequency that's between 640x460 and 800x600 (such as 800x564 pixel as mentioned in TWEAK readme file)

In VGA, on DOS you're almost always using 640x480 or 640x400 (games in 320x200 get doubled).
While text-mode technically has a resolution of 720x400, the monitor gets same timings as for 640x4?0..

EGA on the other hand, while technically 640x350, gets displayind centered in a 640x400 resolution (on VGA cards).
Real non-VGA resolutions, such as 320x200, 640x200, 640x350 and 720x348 might be displayed in hardware emulation modes of SVGA cards (via mode utilities).

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 2 of 3, by anetanel

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Jo22 wrote on 2020-06-18, 06:21:

These old monitors, - I once had a similar one by IBM (PS/2 line) -, are not multisync but rather single-frequency.

That is very interesting. I will try to find more information on my monitor, but it makes sense now.
Thanks!

Reply 3 of 3, by Jo22

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You're welcome! 😀

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

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