Issues With Dreamcast on old Sony Trinitron PVM

One of the projects I've temporarily shelved to focus on other things has been bugging me, and I believe someone here might have an idea how to sort it out.

Here's the setup:
VGA modded Dreamcast fed into Extron RGB 160xi, and then connected to a Sony PVM-1344Q over BNC with RGBS.

The problem is that my monitor is splitting the image and flickering, much like you would see on a monitor failing to sync with a signal of resolution much higher than it expects.

Here's a picture:
https://lh4.googleusercontent.com/-...AAAAAAAB2U/4wTCTVopC-Y/s0/WP_20140505_013.jpg


My thoughts:
I've been reading up on downscaling video properly for displays such as this one, and it appears that the Extron RGB interfaces (including mine) offer the possibility of "DPSS" or Digital Display Sync Processing which one can use to force 240p from a 480i signal (as explained here: http://scanlines.hazard-city.de/). However, this DPSS setting has no effect on the image pictured above. It could be the case that I'm seeing progressive scan signal coming from the DC, and DPSS is only useful for interlaced signals, but regardless I'm interested as to how this could be resolved.

Very soon I'll be getting a NEC PC9821 in, and the only monitor I have on hand capable of displaying horizontal sync at 24kHz is this very PVM. It may work, I have heard, by using generic NEC drivers to drive the display. If I can learn what is going on with the Dreamcast (essentially my attempt at simulating the input of the PC98, in lieu of using another VGA signal) it may make my work much easier in the near future.

 

Try a SCART cable with BNC adapter. Native 15khz from the console should look better than downscaling 480p to 240p or 480i. (haven't seen Dreamcast 15khz mode myself)

 

Thanks for the tip. I'll pick up a VGA to BNC RGBHV cable. It's the same idea, we'd just be bypassing the Extron. The "downscaling" is really just skipping every other line, it should look just fine (at least according to the hazard-city site).


If anyone has ideas as to what causes this kind of tearing/split image, I'd still be very interested to hear, as well as any other advice.

 

I owned a PVM-1344Q and it only accepts 15 KHz.

 

Welp. That's depressing.

I'm still eyeing some scan converters, s-video will do until then.

What did you end up doing?

Edit: If I picked up a scan converter such as this one, do you think it might work?

http://www.ebay.com/itm/VGA-To-RGBS...743?pt=LH_DefaultDomain_0&hash=item2c716c0977

I'm not sure how the PVM will handle 480i at 15kHz. If my Extron interface does indeed not alter the sync rate (it should not), accepts the 15.75kHz CGA signal (it should) and allows me to use the DPSS setting, I may be able to force 240p.