Strange problem with the simple Composite Video Mod on a 4 Switch Atari2600

[ndary]

Hi,

 

Maybe this topic has been covered before, if so i would appreciate if some one could direct me to the correct thread.

 

I did the simple A/V Composite Mod that is show in the following document on a 4 Switch PAL ATARI 2600 : http://www.coolretroprojects.com/atari_2600_av_mod_installation_guide.pdf

 

The Problem is that not on every TV i see a picture, on one TV i see the image clear and fine, and on another i get no image at all!?!?!

 

I installed the same A/V Composite Mod on a 6 Switch Atari 2600 and this machine can show the image on all TV's?? very strange???

 

I replace the RCA Cables, tried another Composite Mod PCB, even tried another ATARI 4 switch console and got the same result, on two 6 Switch Atari 2600 that i tested the video is shown on all TV's but on three ATARI 4 Switch console the video is show on some TV fine and on the other shows as "NO SIGNAL"

 

did any one heard about this phenomena?

 

 

[EvoMikeUK]

Hi,

 

Maybe this topic has been covered before, if so i would appreciate if some one could direct me to the correct thread.

 

I did the simple A/V Composite Mod that is show in the following document on a 4 Switch PAL ATARI 2600 : http://www.coolretroprojects.com/atari_2600_av_mod_installation_guide.pdf

 

The Problem is that not on every TV i see a picture, on one TV i see the image clear and fine, and on another i get no image at all!?!?!

 

I installed the same A/V Composite Mod on a 6 Switch Atari 2600 and this machine can show the image on all TV's?? very strange???

 

I replace the RCA Cables, tried another Composite Mod PCB, even tried another ATARI 4 switch console and got the same result, on two 6 Switch Atari 2600 that i tested the video is shown on all TV's but on three ATARI 4 Switch console the video is show on some TV fine and on the other shows as "NO SIGNAL"

 

did any one heard about this phenomena?

 

 

I find this mod very unstable and unreliable across models and tvs myself. I did it on one Junior which refused to work outright. Its a crude hack. Might be worth investing in a different mod.

[Swami]

Hi,

 

Maybe this topic has been covered before, if so i would appreciate if some one could direct me to the correct thread.

 

I did the simple A/V Composite Mod that is show in the following document on a 4 Switch PAL ATARI 2600 : http://www.coolretroprojects.com/atari_2600_av_mod_installation_guide.pdf

 

The Problem is that not on every TV i see a picture, on one TV i see the image clear and fine, and on another i get no image at all!?!?!

 

I installed the same A/V Composite Mod on a 6 Switch Atari 2600 and this machine can show the image on all TV's?? very strange???

 

I replace the RCA Cables, tried another Composite Mod PCB, even tried another ATARI 4 switch console and got the same result, on two 6 Switch Atari 2600 that i tested the video is shown on all TV's but on three ATARI 4 Switch console the video is show on some TV fine and on the other shows as "NO SIGNAL"

 

did any one heard about this phenomena?

 

 

Here is a similar thread concerning a similar mod on a ColecoVision. I also discuss my experience with a 2600 Junior modded with the basic AV board. Even when a picture appears on a CRT, it often doesn't fill the whole screen and there is an odd blocky black border on one or more sides. I understand there are components missing from this board which stabilize the signal many CRTs are sensitive to.

 

http://atariage.com/forums/topic/270374-retrofixes-cv-mod/

[ndary]

can it be that the video signal level in the 4 switch is lower then the 6 switch? and that's is the reason for the problem?

[ndary]

I swapped out the 2.2k with a 4.7k ohm resistor and the 3.3k with a 6.8k ohm resistor, now the image is shown in the screen i could not see before but the picture is very blury

 

 

[SignGuy81]

yes, the video signal is too weak for some TVs to recognize. A composite video signal should be 1Vpp but it isn't with the mod. Some TVs will accept it anyway but others will not.

[SignGuy81]

http://atariage.com/forums/topic/264563-no-picture-composite-mod/

 

You will see I ran into same issue as you, in trying to get a stronger signal I also introduced more ghosting. I was going to return to that awhile back but never got around to it. I am so tired when I get off work and then have so much stuff that has to be done on the weekends plus want to relax some from work I hardly ever get around to doing things I set out to do.

Edited October 26, 2017 by SignGuy81

[hizzy]

i will co-sign the electronic sentimentalities board. It's really good.

[Osgeld]

the strength of the signal is "louder" on 6 switch models, with my av amp's i usually use a 1.5k pulldown to the input of the driver (a ths or fms component video buffer) where as the 6's I have to lower it to 1k, so more of the signal gets sent to ground

 

and even then the old 6 switch models like to ghost more than newer ones, or like the one on my desk now, which is a heavy sixer guts in a light six case (which happens) is even worse and I am plonking at it trying to get it clean

[simon.plata]

I swapped out the 2.2k with a 4.7k ohm resistor and the 3.3k with a 6.8k ohm resistor, now the image is shown in the screen i could not see before but the picture is very blury

 

I had same problem with my AV mod. The problem was the coupling impedance and a 150pF capacitor not removed from the board.

 

I decided to design my own video amplifier and it Works well.

 

First I tried with a simple one stage design. Clear and Sharp image but not ful brightness.

 

Then I tried with a two stage and I'm happy with the results. Attached the scree pictures of an CRT TV and a LED TV.

 

If you are interested in try this circuit just let me know and I will post the schematics.