13 ms·

RGB Modding the SG-1000 II Is it worth it?

47 points by zdw 4y ago

Gordonjcp 4y ago
It's possible that even when the boxes were new, the box art would come out a little less saturated than real life because you have to take a photograph with a very long exposure to avoid getting a big scan stripe. I say "a very long exposure", but it's still small fractions of a second - not astrophotography, but maybe 1/10th. Still, with that you'd need to stop down a lot to get saturated colours, and given the mood of the day it's likely they were happy to get something usable and "okay it's fine, ship it".
chongli 4y ago
Seems like the overly saturated output could be fixed by putting a trio of potentiometers on the RGB output and using them to attenuate the red, green, and blue signals until they look good.
- colanderman 4y ago
  You also need a trio of op-amps to buffer the signal, else the pots add extra loading which will introduce artifacts. EDIT: actually, I wonder whether these are source+load terminated signals -- that is very common with analog video signals (e.g. VGA). In which case, if the amplifier the author was using doesn't load-terminate the signals, they will be 2× too large (a factor of ~4.6 intensity) when they reach the ADC. In which case, a ~75 Ω resistor at the end of each wire should do the trick, while also improving signal quality.
  - chongli 4y ago
    Oh yeah! I hadn’t even thought of that. I knew it was common for coax cables but didn’t know about RGB. That makes perfect sense though!
genpfault 4y ago
Down for me, archive: https://web.archive.org/web/20230326161041/https://nicole.express/2023/sg-1000-is-a-stupid-name-why-is-there-no-sg-500.html https://web.archive.org/web/20230326161041/https://nicole.ex...
- nicole_express 4y ago
  Unfortunately the site is broken over IPv6, which seems to cause some issues. Honestly since it's just a static site I should probably just blow away the server and restart it, but I'll do that at some point I'm not on the front page of HN...
dfxm12 4y ago
In general, I think it's worth it if you can't use the console's current video output options or even just to satisfy your curiosity. Otherwise, I like to bring out the old consoles for nostalgia, and fussing around with older video out standards and is part of that. In terms of extra gear, optionally busting out an old CRT for a period appropriate composite or RF look is more simple than dealing with mods and scalers or mods and a PVR.
steponlego 4y ago
It messes with certain effects as the developers intended them, such as the famous waterfall scene in Sonic.
DrNosferatu 4y ago
Pretty cool, however I’m disappointed to see no mention it’s exactly the same hardware as the MSX1. Also, the VDP pins output Component YPbPr. These could be used (almost directly) with a compatible TV.
- nicole_express 4y ago
  Only the TMS9928/9A can output component; all NTSC SG-1000 consoles use either the TMS9918A or the VDP mentioned here. It is still pretty much the same as the MSX1. Different sound chip, less RAM, and some ports are different I think.
  - DrNosferatu 4y ago
    Oh - I meant in the context of PAL!

47 points by zdw 4y ago

It's possible that even when the boxes were new, the box art would come out a little less saturated than real life because you have to take a photograph with a very long exposure to avoid getting a big scan stripe. I say "a very long exposure", but it's still small fractions of a second - not astrophotography, but maybe 1/10th. Still, with that you'd need to stop down a lot to get saturated colours, and given the mood of the day it's likely they were happy to get something usable and "okay it's fine, ship it".

chongli 4y ago

Seems like the overly saturated output could be fixed by putting a trio of potentiometers on the RGB output and using them to attenuate the red, green, and blue signals until they look good.

colanderman 4y ago
You also need a trio of op-amps to buffer the signal, else the pots add extra loading which will introduce artifacts. EDIT: actually, I wonder whether these are source+load terminated signals -- that is very common with analog video signals (e.g. VGA). In which case, if the amplifier the author was using doesn't load-terminate the signals, they will be 2× too large (a factor of ~4.6 intensity) when they reach the ADC. In which case, a ~75 Ω resistor at the end of each wire should do the trick, while also improving signal quality.
- chongli 4y ago
  Oh yeah! I hadn’t even thought of that. I knew it was common for coax cables but didn’t know about RGB. That makes perfect sense though!

genpfault 4y ago

Down for me, archive: https://web.archive.org/web/20230326161041/https://nicole.express/2023/sg-1000-is-a-stupid-name-why-is-there-no-sg-500.html https://web.archive.org/web/20230326161041/https://nicole.ex...

nicole_express 4y ago
Unfortunately the site is broken over IPv6, which seems to cause some issues. Honestly since it's just a static site I should probably just blow away the server and restart it, but I'll do that at some point I'm not on the front page of HN...

dfxm12 4y ago

In general, I think it's worth it if you can't use the console's current video output options or even just to satisfy your curiosity. Otherwise, I like to bring out the old consoles for nostalgia, and fussing around with older video out standards and is part of that. In terms of extra gear, optionally busting out an old CRT for a period appropriate composite or RF look is more simple than dealing with mods and scalers or mods and a PVR.

steponlego 4y ago

It messes with certain effects as the developers intended them, such as the famous waterfall scene in Sonic.

DrNosferatu 4y ago

Pretty cool, however I’m disappointed to see no mention it’s exactly the same hardware as the MSX1. Also, the VDP pins output Component YPbPr. These could be used (almost directly) with a compatible TV.

nicole_express 4y ago
Only the TMS9928/9A can output component; all NTSC SG-1000 consoles use either the TMS9918A or the VDP mentioned here. It is still pretty much the same as the MSX1. Different sound chip, less RAM, and some ports are different I think.
- DrNosferatu 4y ago
  Oh - I meant in the context of PAL!