7800 Video Mod...here we go again?

[SoundGammon]

Hi all,

I was just looking at the diagrams for the 400/800/800XL/130XE computer video outputs and I thought I'd pass along a couple of observations.

1) The 400 used a "summing network" with resistors and NO diode on the sync output, just like the 7800.

2) The 800 used a more extensive output with a dual transisitor drivers on the chroma circuit alone! Everyone always said the 800 had the best pic output.

3) The 800XL was cut down and didn't even have a separate chroma output. Easily modified.

4) The 130XE uses a slimmed-down version of the 800 and the SAMS photo-fact doesn't show the chroma output.

 

I'm going to have a friend scan the different video sections so I can upload them and maybe we could use them in our mods.

[Rybags]

Some people seem to say the 130XE has better quality than the 800XL but I tend not to agree.

 

The 400/800 seem to also gain some advantage from their much more extensive sheilding although at the time it was more aimed at suppressing RF from the computer rather than protecting the computer itself.

 

AFAIK, all 130XEs had chroma - mine does, my 800XL didn't until I added it.

[mimo]

some 800xl's had chroma, but they are in the minority, and it is an easy fix. There is also an easy video upgrade that enhances the 800xl s-video and composite video a lot, I would say upto 800 standard.

I bought a 130xe on the strength of people saying it had great video output, but like Rybags I did not like it.

the 400 only has rf output. There is a mod for s-video upgrade but I have never been able to get it to work.

Atari 400 video upgrade

[Rybags]

The problem with a lot of video mods around is that they're designed for NTSC systems, and don't always translate well to PAL.

[puppetmark]

Some of the circuits may be applicable but Rybags is right, most of them are designed for NTSC.

 

BTW, The 130XE uses the video amps in the RF modulator to amplify the composite video signals so it may appear to be more simplified than it is.