New(ish) Video Mod

[A.J. Franzman]

A.J. Franzman's Atari VCS Composite Video Modifications

This is a mod I began working on many moons ago, shortly before Ben released his second version video mod. You can read a little more about it here: Oops! & New Video Mod

@Ben: If you want to incorporate this mod into your site, you are free to do so as originally promised in the other thread referenced above. This includes use of my images, and of course you are free to make more images, for example if you wanted to illustrate the video amplifier circuit or the optional steps with photos. You may use my HTML and text or rewrite any or all of it as you desire; all I ask is that the original design be credited in my name.

[usbcd36]

Cool, how does it compare to the video mods in the sticky here?

[A.J. Franzman]

Well, I haven't done all of them! I would say it's definitely better than either of the 4050 mods (with the IC and with jumpers) as that was what I built first and had problems with. Since I leave the original luma and sync scaling resistors on the mainboard, it needs 2 fewer wires than Ben's new mod (even with my added Blanking wire). I think it's at least as good as both of Ben's mods.

BTW, for anyone who read my mod before the time of this post, I made a couple of resistor value changes to the 3rd optional step (color pot replacement) just now; this will give better adjustment range, as I found that with some mainboards the original version needed the pot to be turned almost all the way to one end.

[usbcd36]

The main thing you should find out is the bang-to-buck ratio of your fully-tricked out mod (expert, all of the optional stuff done) and see how it compares to the really expensive mod the TIA socket thingy. If you could modify it to spit out S-Video, that would be really cool.

Edit: and send it to the guy who made the video mod comparison too, then we can see how it compares to all of the other mods.

[A.J. Franzman]

If someone wants to donate a CyberTech adapter (if that's the one you mean) to me, I'll be happy to do the comparison!
However, bang-to-buck ratios will be hard to compute since I had all the parts needed on hand. I guess if someone had to buy the 9 resistors, pot, cap, transistor and perfboard from Mouser or somewhere it should be around $5 or less, not including shipping. Except for a few of the resistors, they're all common components, and Rat Shack still sells perfboard, so a decent scavenger could build it for next to nothing.

As for S-video, I have no need for it (nothing with S-video input on the front - the TV in the den has it in the back but being a real PITA to get to, and auto-selected whenever there's a plug in it {$#!+#%@ SONY!}, I'm not going to bother with it) but the alteration is really simple - just isolate the chroma signal from luma/sync (+ blank if used), and build a separate copy of the transistor amp for the chroma signal. Some people even say the chroma signal is strong enough as-is, so maybe you could just separate it out as soon as it hits its pullup resistor, and run a wire straight to the C terminal from there.

As far as Nathan Strum's cheeptech.com video mod comparison site, if he wants to add mine to the bunch that's entirely up to him. I'm sure someone will tell him about mine sooner or later. I've seen a couple of other recent mods that aren't on his site yet (including Ben's new one), so I don't even know if the project is still active.

[usbcd36]

Looking over your mod again, I don't see how you're supposed to combine luma, chroma and sync, there is just a video in and out. Are you just supposed to tie them together and input them into the circuit?

[A.J. Franzman]

Read the whole thing. From Step 3, "Video signal comes from the top end of C215". Luma (x3), Chroma and Sync are already combined on the Atari board, so why separate them then recombine them again like everyone else has been doing for so long? The only mention I could find of anyone even trying it this way said it didn't work. Well, whoever it was didn't think to disconnect the RF modulator!

Anyway, since it was confusing to you, I clarified the text a bit.