Service manual for Hyundai HCM-1420 EGA monitor

[keropi]

Hello, as per topic I am searching for the service manual for a Hyundai HCM-1420 EGA monitor that I have (maybe even the user manual if it explains some things...)





For example I don't know what the difference between V.SIZE I and II is (or H.HOLD I and II) or how to enlarge the screen horizontally. There is a pot for Vertical Size but not for horizontal one

Any help tips will be greatly appreciated, thanks in advance!

 

[pcdata76]

Since EGA monitors are also able to sync 200-line (15 kHz) CGA mode, most of the monitors have separate adjustments for CGA and EGA modes. "I" controls adjust for CGA (15 kHz), "II" for EGA (21kHz) mode.

Adjustment for the horizontal size should be inside of the monitor as a variable potentiometer or coil labeled as H-SIZE, H-WIDTH, HOR-W or something similar, but i think monitor is intentionally adjusted at the factory for smaller raster (picture) as in the case with the early CRT's, since convergence and focus drifts off too much at the edges and corners of the CRT. If you enlarge the raster, focus at the corners may not be satisfactory enough (I've done it on my IBM 8513 VGA monitor and that was the result).

 

[keropi]

Thank you so much for the info, really helpfull!
I have noticed this focus/convergence issue you mention, I tried to correct it but no setting worked. I was thinking of recapping the monitor but now after the help you provided I won't even bother with H-Size.
thanks again!

 

[pcdata76]

You're welcome.

If overall focus is a bit off, then you can adjust it from the potentiometer on the flyback transformer after letting the monitor warm up at least half an hour. But due to the age of the monitor, you may not obtain perfect focus. Focus at the corners and edges are usually worse then the center, it is an issue by design so it is not possible to get perfect focus entire screen by adjustment. From the pic you've provided, i don't see any convergence issue so i recommend you to not bother with convergence alignment, which is a quite challenging job.

PS-Since focus adjustment has to be done while monitor is operating, keep your hands away from the circuit board and especially from the thick red wire and suction cup connected to the picture tube.

 

[keropi]

I do have the focus issue on the screen edges, already tried the FOCUS pot on the LOPT but it did not help. Since it's just "the way it is" I simply won't bother, it's only noticeable if you look for it in text mode anyway

thanks again for the great info !

 

[musicforlife]

I have this same EGA monitor and even with max brightness the picture is still so dark that it's uncomfortable to play. Did you open your monitor? Is there brightness trimmer inside so I could remedy this issue? Can you adjust it while it's standing on table?

I used my multisync monitor as reference, though it's quite difficult to take a proper photo to show the difference properly.

 

[pcdata76]

If there is a sub-brightness potentiometer somewhere else on the main or CRT board, first try to correct the issue by adjusting it. Otherwise, you can increase brightness by adjusting the screen potentiometer on flyback transformer, but it may affect the black level negatively and can make retrace lines visible on screen if it is already on the limit.