Demo Vision

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

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seijurou
Posts: 9
Joined: Tue May 24, 2022 3:42 am

Re: Demo Vision

Post by seijurou »

Hello all
I finally get some time this weekend to remove the glue of the 2 screws in battery space, but i can¨t open the gameboy, is like is glued inside too in the area of the wires is solder, if some one some info about how open it just let me know.
coreace
Posts: 2
Joined: Sat Nov 19, 2022 9:19 am

Re: Demo Vision

Post by coreace »

Good info!
Last edited by coreace on Sat Nov 19, 2022 11:38 am, edited 1 time in total.
coreace
Posts: 2
Joined: Sat Nov 19, 2022 9:19 am

Re: Demo Vision

Post by coreace »

My DB2...
20221119_150925_copy_2136x3000.jpg
Last edited by coreace on Sat Nov 19, 2022 11:43 am, edited 1 time in total.
Fiskbit
Posts: 890
Joined: Sat Nov 18, 2017 9:15 pm

Re: Demo Vision

Post by Fiskbit »

Hey, nice to see another one of these!

Does the Game Boy unit on yours open up, or is it glued shut like seijurou's? I'm really hoping to get a better image of where the various wires on the cable connect inside the Game Boy so I can document the pinout on the wiki. With the existing image in the first post of this thread, the order of the wires is about 50% guesswork, which isn't good enough.
Voodooween
Posts: 2
Joined: Sat Nov 26, 2022 2:05 pm

Re: Demo Vision

Post by Voodooween »

Here is some information people could find useful about the Demovision and the Demo Boy II. I recreated the Setup Instruction for both unit and here is the pinout for the Game Boy controller.

Edit : I am also adding the original images I used for the Setup Instructions "repro" I made.
Attachments
G01009132_04_mainboard_back (1).jpg
Demovision_Manual.jpg
Demo_BoyII_Manual.JPG
DemoVision_Manual - Copie.png
Demo_BoyII_Manual.JPG
thisisadam
Posts: 6
Joined: Thu Jan 26, 2023 1:16 pm

Re: Demo Vision

Post by thisisadam »

Hey all -

Came across this forum as i was working on my two DemoBoy II units. I collect nintendo stuff and displays and recently came across them. I only had one GB itself for the DBII, so i was able to take an old GB and solder in a ribbon cable which i purchased online, allowing me to have now two, working, GB units that work with the DBs.

The question however for the group is that one of my DB2's is NTSC, and the other is PAL. The NTSC one works well, however the PAL /EUR version - i purchased a power/voltage converter, as well as a PAL to NTSC RCA cable converter. When i try to use the PAL DB2, the audio comes through to the TV, however visually I just see on screen a black square with a white border.

Opening up the DBs they look fine, no issues. I tried a few things like swapping the boards, power boards, different cables, etc. It seems either A) the PAL DB2 just has a problem, or B) there is some other EUR setting or video different i am not accounting for. I even tried swapping the U46 Chip which was labeled PAL, haha - and that didnt change anything. I did also try both connectors, the RF switch as well as standard RCA cables. I may try swapping out other chips that are easy to hot-swap, as if i could determine if there was a bad chip, i would be able to burn/replace....

Any thoughts welcome! I can provide pics as well if anyone is interested.

Thx again -
Adam
Fiskbit
Posts: 890
Joined: Sat Nov 18, 2017 9:15 pm

Re: Demo Vision

Post by Fiskbit »

Can you try connecting the PAL unit to a modern TV? I believe modern TVs typically support both NTSC and PAL. If it works there, I'd question the converter device.

The PAL chip is PAL as in "Programmable Array Logic", not as in "Phase Alternate Line" video. That chip contains some of the secret sauce that makes the Demo Boy work.

I imagine you could convert the PAL unit to NTSC if you really wanted to, probably just by swapping the socketed CPU and PPU for their NTSC equivalents and presumably changing out the crystal. As these systems are kind of rare, though, I'd suggest leaving it as-is (EDIT: or maybe socketing the crystal so it's easy to swap it back and forth). I don't think I'd expect anything else to differ between NTSC and PAL systems, though because these aren't yet well-understood, I can't say that confidently.
thisisadam
Posts: 6
Joined: Thu Jan 26, 2023 1:16 pm

Re: Demo Vision

Post by thisisadam »

When I try to connect the PAL unit to a modern USA /NTSC TV, or an old CRT - the visual is black and white. This is normal from what i gather due to the differences. With the black and white, i see the same - the greyish border, and black square in the middle with 'noise' in the center.

When I use the converter, the video shows green so it appears the converter is working fine.

I would prefer not to convert the unit, or break it in any way, however would like to see if i could get it working here in the USA truthfully. Do you know which are the chips that you think I would need to swap? Truthfully I am not sure if the issue is one of the existing chips and something is indeed broken, or, if it is just that even with the converters, the video isnt outputting properly ;/

Appreciate the help!
Adam
Fiskbit
Posts: 890
Joined: Sat Nov 18, 2017 9:15 pm

Re: Demo Vision

Post by Fiskbit »

You likely just need to swap the CPU (RP2A07 -> RP2A03 E, G, or H), PPU (RP2C07 -> RP2C02 E, G, or H), and the crystal (26.601712 MHz -> 21.477272 MHz). I believe the former two are socketed by default, so the crystal is the only part that would have to be desoldered, and I suggest socketing that if you can.

Have you tried resetting the system 1 or 2 times after powering it on? It is apparently common for it to need a couple resets before it starts working properly. The exact reason isn't known, and it appears to have been fixed in the revision B firmware.
thisisadam
Posts: 6
Joined: Thu Jan 26, 2023 1:16 pm

Re: Demo Vision

Post by thisisadam »

Thanks for the help. Unfortunately not a 'reboot a few times' issue which the NTSC model DOES do. This PAL/EUR model regardless how how many time I reboot, does this haha.

Which one is the ' crystal'? that is the chip with the exposed window? All of these seem socketed - see the 4 i circled (see attached) in red. Right image is EUR with left being NTSC. I was thinking maybe i could try swapping these out ( all together or one at a time) and if the EUR one starts working... i know which one or which few i can reburn...
Attachments
Right_EUR.jpg
Fiskbit
Posts: 890
Joined: Sat Nov 18, 2017 9:15 pm

Re: Demo Vision

Post by Fiskbit »

The crystal is the two-pin object on the lower right that is blue in the left photo and red in the right photo, with the clock speed printed on it. It is not socketed right now, but I believe socketed crystals are a thing. The two other chips you indicated that are not the CPU or PPU are ROM chips and should be left alone. (Though I suggest covering the exposed window with something opaque, such as electrical tape. While they're more resilient than people tend to think, exposed windows still risk data loss.)

Just to be clear, when you say 'reboot a few times', do you mean turning it off and on, or actually resetting? There is a reset feature and that is what should be used. I don't own a Demo Boy and don't know how to trigger the reset.
Joe
Posts: 649
Joined: Mon Apr 01, 2013 11:17 pm

Re: Demo Vision

Post by Joe »

thisisadam wrote: Thu Jan 26, 2023 3:53 pmI was thinking maybe i could try swapping these out ( all together or one at a time) and if the EUR one starts working... i know which one or which few i can reburn...
Or if the NTSC one stops working.

Swapping the ROMs (the smaller chips with stickers) between units should be a pretty reliable test. If that fixes the PAL unit or breaks the NTSC unit, the ROM is probably bad.

Swapping the CPUs or PPUs (the bigger chips without stickers) between units might not be a reliable test. Without a matching CPU/PPU/crystal, the timing will be incorrect, so it's harder to tell whether the chips are actually broken or just misbehaving due to the timing difference. I'd still try it though - if your TV can display the signal, it'll be helpful for troubleshooting.
Fiskbit
Posts: 890
Joined: Sat Nov 18, 2017 9:15 pm

Re: Demo Vision

Post by Fiskbit »

The system should still work with a bad CHR-ROM, and the PRG-ROM is apparently working enough to draw the border and set the palette, so it's probably functioning properly.

The described symptoms sound like what happens when it's powered on but hasn't been reset a couple times. Unfortunately, I don't have any idea what is going on when it's in that state.
lidnariq
Posts: 11429
Joined: Sun Apr 13, 2008 11:12 am

Re: Demo Vision

Post by lidnariq »

Please provide video of what goes wrong.

Swapping between 50Hz and 60Hz behavior should not be necessary - that should have no effect on whether the DemoVision/DemoBoy successfully captures video from the handheld.
thisisadam
Posts: 6
Joined: Thu Jan 26, 2023 1:16 pm

Re: Demo Vision

Post by thisisadam »

Thanks all.

I will try swapping out the ROMs. Before doing that - see attached this is what happens.

1. If I plug the EUR model in, using power and audio/video converter - i see colors, but empty box in the center (video attached). Note that if i use the EUR board in the USA chassis, or the EUR chassis, i see the same thing on screen. Greenish border and the box in the centerr. Note that without the converter, i just see a greyscale version of everything which is expected.

2. With my USA/NTSC system, i turn it on, reboot a couple of times (power switch) - and i get a picture and the Gameboy bezel design and the game playing. Interestingly, sometimes when i boot up the NTSC usa model, i see the same as above, however rebooting a couple times fixes it. It doesnt fix it here with the PAL/EUR model.

https://drive.google.com/file/d/1kooj6d ... sp=sharing here is the video!
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