Atari 2600 A/V Mod problem (NTSC - 4 switch)

[fujisama]

Hello Atari owners and modders.

 

I'm trying to add an audio / composite output on my "new" atari 2600 (NTSC 4 switch), but I can't obtain any image...

The console worked yesterday with RF output, but with no sound and a really weird/dirty b&w image.

That's why I decided to add an A/V mod to permanently solve the problem. I think I choose the cheaper solution: 2 resistances and 1 transistor, similar to the easier-7800-composite-video-mod

 

My circuit is the same as the solution proposed by brighty83 for a PAL version here (down of the page):http://retro.mmgn.co...ari-2600-AV-Mod

I found the same cicuit on ebay, sellers detail the process on their installation guides for NTSC versions:

http://rover.ebay.com/rover/1/711-53200-19255-0/1?ff3=4&pub=5574883395&toolid=10001&campid=5336500554&customid=&mpre=http%3A%2F%2Fwww.ebay.com%2Fitm%2FAtari-2600-7800-Composite-Video-Mod-Upgrade-Kit-DIY-%2F300592126324 (see Installation Guides for atari 2600 4 switch)

or

http://rover.ebay.com/rover/1/711-53200-19255-0/1?ff3=4&pub=5574883395&toolid=10001&campid=5336500554&customid=&mpre=http%3A%2F%2Fcgi.ebay.fr%2FAtari-2600-A-V-Composite-Video-Mod-Kit-NTSC-PAL-DIY-%2F181042624250%3Fpt%3DLH_DefaultDomain_0%26hash%3Ditem2a26fb36fa

installation guide: http://www.filedropp...stallationguide (page 10 for NTSC 4 switch)

 

 

Here is the circuit (sorry for the poor image quality):

 

 

 

Video out and GND ---> Video RCA

Audio out and GND ---> Audio RCA

 

As mentionned on guides for NTSC 4 switch, I removed the RF box, Q202 and R209:

 

 

 

The sound works well, but no images, it's so sad...

 

I don't know what to do, and I'm dying about playing with it, in good conditions I mean.

Some of you tried this mod? any idea ?

 

Fujisama

[shadow460]

Have you tried swapping out the TIA? What do you mean by "dirty image"... is it staticy or snowy?

[fujisama]

With RF output, I use an old VCR.

The image was not staticy nor snowy, but it's black and white with noise, whaterver the position of color/b&w switch.

It's playable, but not the same taste as flashy atari colors !

 

What do you mean by swapping out the TIA ?

I don't know if there is a pin on the TIA to carry crominance and luminance as composite video signal.

 

I tried to add a 68ohm resistor between video output and gnd like the atari 7800 mod, no effect.

Edited March 13, 2013 by fujisama

[fujisama]

up

[yllawwally]

Do you have a multi-meter? You might have bad caps or a bad 7805. It's easy to check the 7805. On the main board there will be a 7805, it has 3 legs. You need to check the voltage, between the center leg and the other legs. One leg will be about 9v, and the other will be 5v. If it's below 4.95v, then the 7805 should be replaced.

[fujisama]

Yes! It works!

 

I checked my 5 volt pin (initialy connected to the RF box) with my xprotolab.

I don't kwow why, but 5v was low (aprox. 1V) and noisy, (it may explain the poor quality with RF output).

 

So i took 5v directly out the 7508, and --> works fine.

It's wonderful to play on a big HD screen Oo

 

Thank you !

[R.Cade]

Did you have a problem where this mod has the video kind of dark and the color contrast a bit off? I did this and many games look great, but Pac-Man, for example, has contrast issues.

[Yar90]

On 4/12/2013 at 3:54 AM, fujisama said:

Yes! It works!

 

I checked my 5 volt pin (initialy connected to the RF box) with my xprotolab.

I don't kwow why, but 5v was low (aprox. 1V) and noisy, (it may explain the poor quality with RF output).

 

So i took 5v directly out the 7508, and --> works fine.

It's wonderful to play on a big HD screen Oo

 

Thank you !

I am having exactly the same issue and it seems like you found a fix... did you run the 5v wire from your mod board to the 7508?