60hz games and RGB modded Crts

Syntax · Post by **Syntax** » Tue Aug 29, 2017 9:30 pm

I've been playing with 60hz ntsc consoles the past few weeks and have a question

I have been testing rgb modded pal tv's with a pal 60hz modded Snes. Picture is
fine 50 or 60hz.
But my pal Mega Drive at 60hz and AV famicom has an akb line up the top (slanted deconverged bar)

Why is this? Because ntsc signal on pal tv and akb needs to be tuned off screen?
Also why is Snes fine? Is it actually outputting 50hz but changed res?

theclaw · Post by **theclaw** » Wed Aug 30, 2017 1:24 am

On some consoles, a switch that just toggles 50hz / 60hz is imperfect.
You may need to have the switch also change to the appropriate crystal oscillator.

Syntax · Post by **Syntax** » Wed Aug 30, 2017 1:50 am

Please go into more detail.

I feel your solely speaking of the mega drive and it's inability to put correct color over composite when using switching mods.

This has nothing to do with the topic on hand as I run rgb and comp is only used for sync not color.

Makinx · Post by **Makinx** » Wed Aug 30, 2017 8:47 am

Could you explain what an "rgb modded pal tv" is? I have never had a pal crt that doesn't accept rgb input out of the box (not since the '80s anyway). What model tv do you use?

Also, if you could make a picture of the screen when the problem occurs, that would be helpful.

theclaw · Post by **theclaw** » Wed Aug 30, 2017 12:03 pm

Syntax wrote:Please go into more detail.

I feel your solely speaking of the mega drive and it's inability to put correct color over composite when using switching mods.

This has nothing to do with the topic on hand as I run rgb and comp is only used for sync not color.

issues are rarer with rgb, but can happen. you are still running the system slightly out-of-spec by using the pal oscillator.

Syntax · Post by **Syntax** » Wed Aug 30, 2017 9:01 pm

Makinx wrote:Could you explain what an "rgb modded pal tv" is? I have never had a pal crt that doesn't accept rgb input out of the box (not since the '80s anyway). What model tv do you use?

Also, if you could make a picture of the screen when the problem occurs, that would be helpful.

Pretty much 99% of all TVs sold in Australia have no scart, usually just a single composite plug or if your lucky component.

You ask what model, but I have many, Quintrix, Trinitron powervision ect

What Ive found is I don't seem to have this problem with the sony range, they have the AKB feature which pulls this line off screen at all times.

I mostly want to find out why this line occurs and why my snes wont make it happen at 60hz.

Syntax · Post by **Syntax** » Wed Aug 30, 2017 9:29 pm

theclaw wrote:
issues are rarer with rgb, but can happen. you are still running the system slightly out-of-spec by using the pal oscillator.

Care to explain what issues?
(I'm sure they are not related to the topic but I'm interested as I haven't seen any compatibility issues with a megadrive 60hz modded unless your playing PAL optimized games).

Makinx · Post by **Makinx** » Wed Aug 30, 2017 10:54 pm

Syntax wrote:

Pretty much 99% of all TVs sold in Australia have no scart, usually just a single composite plug or if your lucky component.

Ah I wasn't thinking about Australia, just Europe. I'm afraid I have no experience with Australian sets. sorry. At any rate, I can't reproduce your problem on any of my pal crt's with the same consoles.

theclaw · Post by **theclaw** » Wed Aug 30, 2017 11:17 pm

Syntax wrote:
theclaw wrote:
issues are rarer with rgb, but can happen. you are still running the system slightly out-of-spec by using the pal oscillator.
Care to explain what issues?
(I'm sure they are not related to the topic but I'm interested as I haven't seen any compatibility issues with a megadrive 60hz modded unless your playing PAL optimized games).

Video sync timing, I don't understand all the details myself. In any event a megadrive modded to 60hz isn't identical to an ntsc megadrive.

Easiest to look at a picture of the mainboard. NTSC systems have a 53.693MHz chip, where PAL systems have 53.203MHz. Some devices like XRGB are more sensitive to the difference than regular TVs.

Syntax · Post by **Syntax** » Thu Aug 31, 2017 12:28 am

theclaw wrote:
Syntax wrote:
theclaw wrote:
issues are rarer with rgb, but can happen. you are still running the system slightly out-of-spec by using the pal oscillator.
Care to explain what issues?
(I'm sure they are not related to the topic but I'm interested as I haven't seen any compatibility issues with a megadrive 60hz modded unless your playing PAL optimized games).
Video sync timing, I don't understand all the details myself. In any event a megadrive modded to 60hz isn't identical to an ntsc megadrive.

Easiest to look at a picture of the mainboard. NTSC systems have a 53.693MHz chip, where PAL systems have 53.203MHz. Some devices like XRGB are more sensitive to the difference than regular TVs.

I'm not sure how the Snes timing works with the 60hz mod but I do understand the crystal timing difference on the Sega. That said:
My A/V Nes is native 60hz. Shows the line up top.
My mega drive is native pal. Shows line at top in 60hz mode.
My Snes is native pal. Shows no line at 60hz.

What is the common denominator here causing the line?

werk91 · Post by **werk91** » Fri Sep 01, 2017 5:56 pm

I had to buy a new NTSC Sega Genesis because my JVC PVM would not even sync properly with the PAL MegaDrive modded with 60hz switch. It wasn't a bad image quality or anything, it was unplayable shaky mess. All other screens work fine with it.

Lawfer · Post by **Lawfer** » Fri Sep 01, 2017 6:02 pm

Some PAL TVs can't do 60hz, but most of them do.

And RGB modded CRTs? Most PAL TVs could do RGB through scart.

Makinx · Post by **Makinx** » Mon Sep 04, 2017 9:24 am

Lawfer wrote: And RGB modded CRTs? Most PAL TVs could do RGB through scart.

In Europe, yes. In Australia not so much.

Lawfer · Post by **Lawfer** » Mon Sep 04, 2017 4:31 pm

Makinx wrote:
Lawfer wrote: And RGB modded CRTs? Most PAL TVs could do RGB through scart.

In Europe, yes. In Australia not so much.

Can't he just get a European TV then? Australia is 240V/50Hz, a European TV will work no problem.

speedlolita · Post by **speedlolita** » Mon Sep 04, 2017 5:17 pm

Lawfer wrote:
Makinx wrote:
Lawfer wrote: And RGB modded CRTs? Most PAL TVs could do RGB through scart.

In Europe, yes. In Australia not so much.
Can't he just get a European TV then? Australia is 240V/50Hz, a European TV will work no problem.

Shipping a CRT across the world is kinda risky and expensive unless absolutely necessary.

Syntax · Post by **Syntax** » Wed Sep 06, 2017 12:26 am

Wow, ok we kinda missed what I was asking guys
I have like 20 crts here at the moment, getting a good picture in RGB is not the problem.

I am asking why only some of these systems create an intense rainbow scanline on the top of the screen in 60 hz mode.
Av Famicom does it.
Modded pal Sega with pal crystal does it.
BUT

Modded pal Snes DOES NOT CREATE THE LINE.

So what the Snes do differently to the Sega in 60hz mod mode (No crystal swa)

shmups.system11.org

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