Help Tweaking Timings Video Mode on CRT

[Slypty]

For the past few months, I've been exhausting myself with different .ini files to use with my CRT. It's a 15Khz (240p) Sony KV-25DXR which I am able to get a nice picture with. The only issue is the rolling 'fuzz' that the menu does on any MiSTer appears in a red tinge. This rolling of red happens on any system, any game and it just gets annoying. I also don't want to wear out my red gun if I can avoid it.

Currently, the BEST video settings I've been able to establish are:
video_mode = 384, 31, 25, 71, 224, 12, 3, 23, 8040

So I'm happy with the 384x224 resolution, it matches my screen very well. I'm wondering if there's some way to tweak the back or front porch timing to avoid this red image.
I've also found this video mode to look sharper and with much less 'red', but about 1/4 of the screen is chopped off at the top:
video_mode = 512,42,62,64,224,11,21,6,10689

I'm a bit of a noob when it comes to playing with anything other than resolutions, and even changing those usually fail. Is there any advice in understanding what's causing the redness, or what I could do in the settings to avoid it? I can rule out the MiSTer or my setup as a problem, with other consoles using the same setup I have good results.

PXL_20220315_172636115.jpg (4.9 MiB) Viewed 2230 times

[akeley]

Please describe how are you connecting your MiSTer to this TV. You shouldn't need any custom modelines to achieve perfect image in most cases.

[Slypty]

Please describe how are you connecting your MiSTer to this TV. You shouldn't need any custom modelines to achieve perfect image in most cases.

I'm using the VGA Component Cables from the MiSTer Add-Ons Site. Component is then taken to a Trasncoder that outputs SCART. SCART, is then collected to the IDE Cable that this TV accepts for RGB.

I've tried the direct video method using HDMI, but I don't achieve a signal. Also, setting the Default I/O Video Mode to 0 doesn't produce a valid image, this TV is 15Khz only it seems.

[akeley]

Ah, this is that rather esoteric TV you had posted about before. With a picky unit like that and a complex chain connecting to it, it could be anything really. Well above my paygrade, maybe somebody else has some ideas.

[Slypty]

Well it's safe to rule out the transcoder, VGA Cable, the MiSTer itself and my IDE ribbon cable. Using a Wii with the same setup, I have a perfect visual, and my Saturn works just fine using just the same IDE cable.

The only clue I have, is that if I set the resolution to 512, the redness NEARLY goes away.. that would be with the video code I left above that starts with 512. Maybe there's some clues in there that may shed some light on what's going on.

[FoxbatStargazer]

You say it prefers luma for sync, isn't that the same as Sync on Green? A VGA->RGB Scart cable plugged directly into the Mister I/O board, and with the SoG switch flipped on, should output that. (It will also continue to output standard sync line, so you should go with a cable with sync resistor for safety, or else somehow block the sync pins entirely.)

[Slypty]

You say it prefers luma for sync, isn't that the same as Sync on Green? A VGA->RGB Scart cable plugged directly into the Mister I/O board, and with the SoG switch flipped on, should output that. (It will also continue to output standard sync line, so you should go with a cable with sync resistor for safety, or else somehow block the sync pins entirely.)

Right, but in order to use this TV that has an RGB input that depends on a floppy IDE pinout, my only choice is to transcode it to SCART before I send it to the TV. The same process takes place with my Wii with no adverse affect on the signal. I haven't tried adding a resistor yet so I will try that

[akeley]

Well it's safe to rule out the transcoder, VGA Cable, the MiSTer itself and my IDE ribbon cable. Using a Wii with the same setup, I have a perfect visual, and my Saturn works just fine using just the same IDE cable.

That doesn't necessarily mean there is no problem. I have TVs/cables which are fine with some consoles and micros, but not with MiSTer.

[Slypty]

[/quote]
That doesn't necessarily mean there is no problem. I have TVs/cables which are fine with some consoles and micros, but not with MiSTer.
[/quote]

The MiSTer runs fine on my PVM directly through the VGA Component cables. I'm ruling out any external hardware performance issues, at least withstanding the possibility that the sync line is probably running luma & sync together. Most likely this CRT reacts differently to the sync pulses of c-sync timings than luma.

I might end up building a sync stripper in to the combined line to pull out c-sync and just terminate it, leaving luma only.

[Slypty]

Update, definitely a CSync issue combined with Luma.

Built an LM1881 sync stripper, and installed it in my scart cable, basically the goal was take out csync from the line. The only way to accomplish that was to put the sync stripper on pin 21 of the scart cable before the output pin, then terminate the csync output so it doesn't feed in to pin 21.

Didn't really see much results. The only time the screen evens itself out, is when I switched the SOG switch off, then On again. The screen levels out for a minute but the red does come back in.

I tried cutting the pin 21 line completely and running direct csync from the output of the sync stripper ( to pin 21 instead of the original combined sync output). The screen rolls horizontally, and red is maintained. So.. me thinks the issue is the CSync on that line.

Long story short, is there any way to have the MiSTer output Luma (only) somehow? Or a proper method of taking CSync out from a combined sync output?