Twin Famicom on a 50" Sony LCD, weird glitches

Twin Famicom on a 50" Sony LCD, weird glitches
by akimaru on 2006-04-05 (#11576)

I just got myself a Sony Bravia 50" 3LCD rear projetion tv. Everything is fine and dandy, except my Twin Famicom (hooked up via composite).

The video has some weird glitches. I took a screenshot to help explaining this. Anyways, there seems to be 2 pictures: the other is a shadow, which causes the colors to have this "pearl" effect. In the middle of the screen is a pearly yellow bar, about 2cm thick. You can see the pearly stuff in the red background of the FDS logo and the yellow in the black background.

The weird part is that all the other older consoles, including my SNES and Genesis, work fine in both composite and RGB on the TV. Just my Twin Famicom is giving me trouble. The console works perfectly on our 21" CRT TV, so the console is fine.

I'm starting to have my thoughts that the "stripey" graphics has something to do with this (The Twin Famicom also suffers from this, like the toploader NES): almost like the Famicom is outputting a way too strong video signal for the tv. Is there a way to fix this?

Any idea what's causing this weird stuff to happen on my new TV? Is it just that the console's way to output composite video makes my tv go bonkers? I can't try switching from composite to RF for 2 reasons: it's a PAL TV, NTSC RF doesn't work. The TV can do every form of NTSC, PAL and SECAM, but not NTSC RF. Plus, an RF cable for Twin Famicom seems to be rare as hell, I've never even seen one.

The picture:

View wide picture

by tepples on 2006-04-05 (#11580)

The glitch above and to the left of "PLEASE" is shaped like the area around "MIC" in "Famicom". This suggests that perhaps the comb filter in the TV's upscaler is designed only for 480i signals and is not suited for the 240p signal that an NES spits out. Do you also have problems with the frontloading NES, the toploading NES, the original Famicom, or the AV Famicom? As for RF incompatibility, you can use an NTSC VCR to translate NTSC/M RF signal into NTSC composite video and audio.

You mentioned that you have a Super NES and Sega Genesis. Only the North American and European consoles were called "Super NES" (other was Super Famicom), and only the North American console was called "Genesis" (others were Mega Drive). This leads me to believe that you are using Japanese consoles on a TV configured to interpret NTSC signals as North American. (The Japanese version of NTSC is mostly compatible with the USA version, except that they use different black levels.) If you're using a TV sold in PAL region, this is likely because PAL/NTSC compatible TVs sold in Europe are likely to be configured to display North American content that the community of English speakers in the UK demands. Does it happen with any other consoles imported from Japan?

Games for the 16-bit systems are also less likely to use large areas of solid colors than games for the original NES/Famicom/Famiclones. Does this also happen in more detailed NES games?

by akimaru on 2006-04-05 (#11584)

tepples wrote:
The glitch above and to the left of "PLEASE" is shaped like the area around "MIC" in "Famicom". This suggests that perhaps the comb filter in the TV's upscaler is designed only for 480i signals and is not suited for the 240p signal that an NES spits out. Do you also have problems with the frontloading NES, the toploading NES, the original Famicom, or the AV Famicom? As for RF incompatibility, you can use an NTSC VCR to translate NTSC/M RF signal into NTSC composite video and audio.

You mentioned that you have a Super NES and Sega Genesis. Only the North American and European consoles were called "Super NES" (other was Super Famicom), and only the North American console was called "Genesis" (others were Mega Drive). This leads me to believe that you are using Japanese consoles on a TV configured to interpret NTSC signals as North American. (The Japanese version of NTSC is mostly compatible with the USA version, except that they use different black levels.) If you're using a TV sold in PAL region, this is likely because PAL/NTSC compatible TVs sold in Europe are likely to be configured to display North American content that the community of English speakers in the UK demands. Does it happen with any other consoles imported from Japan?

Games for the 16-bit systems are also less likely to use large areas of solid colors than games for the original NES/Famicom/Famiclones. Does this also happen in more detailed NES games?

Thanks for the reply. The comb filter -could- be the cause. I can test the TV with a front-loader PAL NES (need to borrow it from my friend first), I'll tell the results when I get my hands on one. The video signal is different on a PAL machine, I'm quite positive that it'll work perfectly.

I have quite a few consoles. I've tested them all on the TV, and here are the results. I tested all the consoles in both RGB (where available) and composite. About the TV: The TV is a PAL multinorm HDTV, it supports PAL and Secam through RF. Through all the composite, HDMI, Component and SCART ports the system supports all the PAL standards, PAL60, NTSC 3.58, NTSC 4.43 and Secam.

American Super Nintendo: RGB and composite work perfectly.
American Sega Genesis: RGB and composite work perfectly.
PAL Mega Drive 2 (with a 50/60hz switch, tried both modes): RGB and composite work perfectly.
Japanese PC Engine DUO: composite works perfectly.
Japanese PC-FX: composite and S-VHS works perfectly.
American Nintendo 64: composite works perfectly.
American PlayStation and Sega Saturn: RGB, S-VHS and composite all work perfectly.

The PC Engine DUO should output at the same resolution (256x224, 240p?) as the Famicom, am I correct? No problems with the DUO... just with the Twin Famicom.

I can take a picture of the Twin Famicom main board and the AV board, if it helps.

I wonder if the http://darthcloud.da.funpic.org/img/bypass.html AV fix would help? If the problem lies in the comb filter (which I'm somewhat positive that it's not the problem here), I need just something to sit between the signals. I tried to put the signal through my VCR, but no-go.

The black background always has the yellow pearl stripe. For example, RAF World (Journey to Silius) has a white main title screen, it's ALMOST perfect. I'll grab a picture tomorrow.

Thanks for all the help guys.. I really appreciate it.

-Akimaru

by tepples on 2006-04-05 (#11586)

The fact that the PC Engine DUO doesn't have the same defect as the NES matters little, as its video DAC may be more like that of the Super NES than that of the NES. (The tile formats sure are )

akimaru wrote:
I tried to put the signal through my VCR, but no-go.

Which VCR? It has to be a North American VCR in order to tune into North American channel 3/4, or a Japanese VCR in order to tune into Japanese channel 1/2.

Quote:
The black background always has the yellow pearl stripe.

A vertical stripe might be an echo of the color burst. If your TV's upscaler can't handle progressive signals in the form that the NES sends them, the color burst might be reflected elsewhere on the scanline.

by akimaru on 2006-04-06 (#11607)

tepples wrote:
The fact that the PC Engine DUO doesn't have the same defect as the NES matters little, as its video DAC may be more like that of the Super NES than that of the NES. (The tile formats sure are )

akimaru wrote:
I tried to put the signal through my VCR, but no-go.

Which VCR? It has to be a North American VCR in order to tune into North American channel 3/4, or a Japanese VCR in order to tune into Japanese channel 1/2.

Quote:
The black background always has the yellow pearl stripe.

A vertical stripe might be an echo of the color burst. If your TV's upscaler can't handle progressive signals in the form that the NES sends them, the color burst might be reflected elsewhere on the scanline.

It's a PAL VCR.. I don't have access to an NTSC one.

I'm going to try a PAL NES today, I'll let you know what happens.

What do you mean by the "defect"? The Famicom sends the 240p signal is some non-standard way?

by tepples on 2006-04-06 (#11612)

akimaru wrote:
What do you mean by the "defect"?

The "defect" is whatever in the video signal produces the artifacts on your TV.

Quote:
The Famicom sends the 240p signal is some non-standard way?

240p itself is nonstandard. The 341-PPU-cycle scanline period is also nonstandard (standard TV uses the equivalent of 341.25 cycles). But the NTSC Super Famicom and Super NES would have the same problem.

Another issue is that at some point in at least the NTSC Super NES's life, Nintendo changed the vsync signal in 240p mode from all even fields to all odd fields or vice versa, possibly to solve image stability problems with some Sony TVs.

Yet another cause could be ghost cancellation processing.

by akimaru on 2006-04-06 (#11622)

I take my word back from the Super Nintendo composite.

I noticed that my Scart divider's RGB on/off button is stuck on RGB (old piece of shit), so RGB was enabled all the time.

I re-tested Genesis, Super Nintendo, PSone and Saturn with their original RCA leads. Genesis, PSone and Saturn all worked fine in composite.

Super Nintendo behaved identically as my Famicom: Yellow pearl stripe and a shadowed image. So, in RGB mode, the TV works normally. Composite Famicom/SNES enables the defect. At least now I know that the Twin Famicom and the american original SNES model function the same way.

Ok.. tepples, what do you think I should do? Start looking for a Playchoice 10 board and do a RGB mod to the Twin Famicom? I'm ready to do all the possible video mods for the Famicom, in case something helps.. I don't have the balls to go and start toying around with the service menu of the TV.. There just has to be a way to fool the de-interlacer or the comb filter...

And thank you again for all the help this far!

-Akimaru