Hantarex Polo 25 - "convergence" problem at 60Hz w/ interlaced image

[krick]

I have a Hantarex Polo 25 monitor running at standard res 15KHz.
I'm running GroovyMAME with Calamity's hacked ATI Radeon drivers and an ATI Radeon X600 XT through an Ultimarc JPAC.
(NOTE that this is not a GroovyMAME problem, it's a hardware problem with my monitor).

I'm having an issue with my monitor when trying to display games with interlaced resolutions at 60Hz.  Basically, if I turn the "Vertical Amplitude" control on my monitor way down, it will display sharp, but somewhat squashed vertically.  If I use the "Vertical Amplitude" control to stretch the image to fill the screen, the image doubles and looks like the interlace has a problem with convergence (not sure if that's the right terminology for what I'm seeing).  Basically, one of the images (even or odd) isn't lining up with the other.  It also shakes/jumps a lot.

I'm not sure if it's just over spec for the monitor, or if there's something wrong with the monitor electronics.  Due to the age of the monitor, I wouldn't be surprised if it needed a good re-capping, but I wanted to get a second opinion as I don't want to take a chance on the cap kit and accidentally kill the monitor, or end up with something worse than I have now.  Other than this one issue, it seems fairly decent.  Note that interlaced games at 50Hz are completely fine.  Progressive games have no issues that I've been able to find.

tempest, asteroid, and astdelux -- GroovyMAME picks: 768x512@60  --  all have the convergence problem.

starwars, cchasm, mhavoc -- GroovyMAME picks: 768x576@50 (or 49.5)  -- all display fine.

Here's more info about the problem with pictures starting at post #18...
http://forum.arcadecontrols.com/index.php/topic,121372.msg1325180.html#msg1325180
(NOTE that I jacked up the brightness/contrast deliberately for these pictures.  I don't normally run it like that.)

[MTPPC]

Your J-Pac is splitting the image because I think that second resolution setting is higher than 15Khz? I don't understand it all, but that's my best guess. Can you manually set the resolution to something else and see if the problem goes away?

[krick]

Your J-Pac is splitting the image because I think that second resolution setting is higher than 15Khz? I don't understand it all, but that's my best guess. Can you manually set the resolution to something else and see if the problem goes away?

It's not the kind of doubling that you'd see from an out of frequency signal going through a JPAC.  That doubles the image side-by-side.  I'm very familiar with that.

My monitor works fine with every other resolution I've tried, progressive or interlaced.   Only interlaced resolutions close to 60Hz have issues, and only if I try to make it fill the screen vertically with my monitor controls.    If you look at the photos in the other thread I linked (click on them to view larger), you'll see the doubling I'm talking about.  It's more of a ghosting effect.  When the monitor is drawing the interlaced signal, the second pass of the electron beam is not lined up with the first pass.

[MonMotha]

How many total lines (NOT visible - TOTAL) are in the mode you're using?  It MUST be odd for interlace to behave correctly.

[Calamity]

All interlaced modes created by GM have an odd number of lines. These are the ones taken from krick's logs:

tempest (bad):
Modeline "768x512_55 16.65KHz 60.00Hz" 16.92 768 800 880 1016 512 514 519 555 interlace  -hsync -vsync

starwars(good):
Modeline "768x576_54 15.67KHz 49.50Hz" 15.67 768 800 872 1000 576 586 591 633 interlace  -hsync -vsync

[krick]

I never found a solution to this problem.  Is this something a cap kit might fix or should I be looking elsewhere?