Nanao MS9-29S Incomplete first scan line

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DaveOrAstroDave
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Nanao MS9-29S Incomplete first scan line

Post by DaveOrAstroDave » February 22nd, 2009, 9:09 pm

Hi Everyone,

I'm having a weird issue with the Nanao in my Astro City cab. The first scan line seems to actually start from about 1/3 of the way accross the screen, and the length of the scan line seems to vary with the brightness of the raster, or the height of the screen as set by the height adjustment pot. In fact, if I have the height set to the minimum possible setting, everything is fine (but squished), but as I increase the height, the top scan line begins to disappear, from left to right. This begins to happen when there is still a black border on the top and bottom of the screen of a couple inches. Any idea what's going on? Is this a sign of impending CRT doom, or is it normal?

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Re: Nanao MS9-29S Incomplete first scan line

Post by grantspain » February 22nd, 2009, 9:16 pm

sounds like just an adjustment issue to me,what is the video input signal ?

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Re: Nanao MS9-29S Incomplete first scan line

Post by DaveOrAstroDave » February 22nd, 2009, 9:31 pm

I've noticed the issue with prettymuch everything I've hooked up. Right now I've got a Mushihimesama PCB connected, but I've also noticed it with ESPGaluda II and my PS2 that I wired a vga-port onto. Actually, I never noticed it with my MAME pc w/ArcadeVGA card, but that doesn't necessarily mean that it doesn't do it too...
If it's an adjustment, what it is that I'd need to adjust?

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Re: Nanao MS9-29S Incomplete first scan line

Post by grantspain » February 22nd, 2009, 9:37 pm

can you post a photo of the problem please

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Re: Nanao MS9-29S Incomplete first scan line

Post by DaveOrAstroDave » February 22nd, 2009, 10:00 pm

It was kinda hard to get a pic, but maybe this will do. The monitor is mounted vertically, so as I adjust the width (height for landscape orientation), I can count up to 3 scan lines gradually disappear, one after another, as the height pot is adjusted, or as the picture gets brighter. Since it's picture dependent, it gives the appearance that the beginning of the scan line is floating.
HalfMissing_ScanLine.jpg
missing_line_2.jpg
What do you think?

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Re: Nanao MS9-29S Incomplete first scan line

Post by grantspain » February 22nd, 2009, 10:03 pm

well i have this strange feeling that this is common with cave games but do not know for sure
there is one adjustment which is vs limit-vertical size limit that may or may not help with this problem

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Re: Nanao MS9-29S Incomplete first scan line

Post by DaveOrAstroDave » February 22nd, 2009, 11:00 pm

Hmm. I was wondering that myself about it being cave-specific, but if that was the case, I don't understand why adjusting the monitor would affect it. It seems like it's got to be something the monitor's doing with the signal, because adjusting the monitor height pot doesn't affect how the PCB generates the signal, right?

In any case, I gave the VS Limit pot a twist, and while it does seem to have some effect, I'm still down about 3 scan-lines by the time the raster is sized to fit the entire screen. I don't know if it's relevant, but the spacing on those 3 scan lines also seems a bit wider than on the rest of the raster, regardless of how the size and position pots are adjusted.

I suppose it's not that big a deal - just the perfectionist in me wanting all the pixels on-screen =)
Still, I wonder if it's the sign of some failed or failing component. Is the electron beam suppressed or shut off while the deflection returns to top-left after finishing a frame? If so, maybe what's going on is that suppression isn't shutting off soon enough when the scanning begins for the next frame?

Anyway, thanks for the input!

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Re: Nanao MS9-29S Incomplete first scan line

Post by grantspain » February 22nd, 2009, 11:11 pm

wow thats a lot of questions,i do know that a 15khz signal from a game board can affect geometry but by the way the monitor processes the signal-and i am sure i have seen similar post from cave pcb owners
now if you had posted the same problem but with a lapover effect on the horizontal i would have said that you have component failure on the vertical deflection somewhere(normally the input smoothing to the vert def ic)

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Re: Nanao MS9-29S Incomplete first scan line

Post by Chi » February 22nd, 2009, 11:16 pm

Grant is spot on the money. I've had the same problem with Cave SH-3 boards (Espgaluda II, Mushihimesama, Death Smiles, etc) on my Egret II's MS9 (as have many people). Move the display down by 1 or 2 pixels using the in-game screen check test menu and it will go away. No idea why it does it, but it is common.
"TO THE untrained eye Christian Cooper might have been stamping out a small fire " - The Times, 7th Feb, 2004

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Re: Nanao MS9-29S Incomplete first scan line

Post by DaveOrAstroDave » February 22nd, 2009, 11:31 pm

Ahah! Now it's starting to make some sense. Perhaps what's happening is the video generator on the cave board is starting each frame too soon, i.e. before the vblank, etc finishes completely. If that's the case, that would explain why moving the image further down via the test menu would help - it delays the beginning of the frame. I'll give that a try and see if it helps!

Thanks!

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Re: Nanao MS9-29S Incomplete first scan line

Post by SuperPang » February 23rd, 2009, 12:15 pm

Yep, this is at least the third thread on this odd SH3 issue :D

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Re: Nanao MS9-29S Incomplete first scan line

Post by markedkiller78 » February 23rd, 2009, 12:48 pm

Was I the first lol,

Death smiles was the one I noticed it most in. Such an easy fix too :awe:
Image

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Re: Nanao MS9-29S Incomplete first scan line

Post by DaveOrAstroDave » February 23rd, 2009, 2:22 pm

Yep, that did indeed fix it.
Sorry to bring this one up for the apparent third time.. I guess I didn't search thoroughly enough.

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Re: Nanao MS9-29S Incomplete first scan line

Post by Chi » February 23rd, 2009, 2:26 pm

It's not an easy thing to search for, tbh (till you realise it is common to Cave SH-3 and isn't just the monitor :P).
"TO THE untrained eye Christian Cooper might have been stamping out a small fire " - The Times, 7th Feb, 2004

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