600XL (composite modded) on a TV

[iast]

Hello. Today I got in a 600XL I won on ebay. The previous owner had modded the console by removing the RF-out socket and replacing it with a 3.5mm phono jack wired for composite video & mono audio. I tested it out on two different CRT TVs and while it works/plays fine and all, I noticed this with the picture on both TVs:

 

http://imgur.com/9x6tCLd

 

Basically, the letters aren't as solid as I was expecting them to be. They have some weird stratification or ghosting effect to them. Now, on his ebay listing, the seller shows it hooked up to a LCD monitor and everything looks much more solid/filled-in:

 

http://www.ebay.com/itm/Atari-600XL-Computer-with-64K-Ram-and-Composite-Video-/131119798001?_trksid=p2047675.l2557&ssPageName=STRK%3AMEWNX%3AIT&nma=true&si=oFvxcWnvVQHVXOVLdK%252BKFvmujAI%253D&orig_cvip=true&rt=nc

 

So what I'm wondering is if this issue I'm getting is due to playing on a CRT television or if there might be something else going on. Thanks.

[gozar]

(Unrelated...)

 

I wanted that 600xl! I didn't want to pay $65 for it though. :-)

[iast]

Alright, on a suggestion I tweaked with the potentiometer under the computer. I can get the screen looking a bit crisper doing that, but it only really gets that way if I turn it enough to make the picture black & white. At this point I'm not sure what to do. The seller did offer to refund me for it though which is nice, but I'd like to explore my options before resorting to that.

[Rybags]

I guess it's NTSC, PAL has the monitor port.

 

S-Video is the best solution, but no idea if there's a project around to add the required circuit to the 600XL.

 

Chances are someone performed a video mod on the machine in addition to removing the RF modulator, but the output should be a lot better than that.

[iast]

It is NTSC. That's exactly how they modded it as you described (it was done by a previous owner, not the one that sent it to me).

[Rybags]

It's like the colour output is too strong. And there's luma dropping out on some character boundaries.

 

Might be a simple case of a couple of components of the wrong spec, but diagnosing someone else's work can be a pain.

[Marius]

I know this on stock pal 600xl

 

There it is as simple as removing one ceramic disc capacitor and the image is brilliant.

 

I could see in my 600xl which cap it is, but I absolutely can not guarantee that this will be a good fix on NTSC.

[iast]

After deciding to keep this, I opened it up to have a closer look. As it turns out, the RF modulator is still inside, or at least the case for it is there.

As you can see in the pictures below (link goes to album), there's three wires coming from the back of the modulator casing. Two are soldered to the PCB right behind it and a longer third one is soldered to the top lead of a resistor. You can also see in the pics the phono jack that sits where the RF jack used to be.

http://imgur.com/a/DxAFp

Edited February 28, 2014 by iast

[Rybags]

The top cover of the RF mod should come off fairly easily - maybe some pics of inside might reveal something.

[iast]

This is what's inside the RF casing.

 

http://imgur.com/a/Pr5Ej

[Roydea6]

This is what's inside the RF casing.

 

http://imgur.com/a/Pr5Ej

This is probably this Mod http://atrey.karlin.mff.cuni.cz/~pavel/atari/600xlmon.html Just stuck inside the RF with a video plug instead of the 5pin Din connector.

[iast]

Hmm, alright. So what would be the best way of proceeding about correcting this? I haven't done much mod work myself before but the 600XL otherwise is in nice shape and I'd hate to get rid of it just because someone's mod wasn't attuned right.

[+bob1200xl]

'Best' way to add a monitor port is to mount all the parts in the m/b the way Atari made it. The hard part is cutting the hole in the case for the jack. I use a hole punch and then ream it out to size with a step-drill.

 

Bob