2600 Jr. - Repair "snowy" video output

[ranger81]

Hi all,

 

I got a used Atari 2600 Jr. and it is having serious issues with the video output. I have tuned my television to the proper channel (checked with another Atari 2600 Jr), but I can only see „snow“.

The „snow“ slightly changes, when I adjust the color adjustment potentiometer and also if I switch the „Channel“ switch. Therefore I assume some kind of output is produced.

Temporarily I installed a Composite mod and I got a video signal (colors were off even though I tried to adjust the potentiometer, but at least I got a signal).

Also tried to adjust the two variable inductors on the RF modulator. The „snow“ changes when turning them, but never get a real video output.

 

Why not just keep the Composite you may ask? Well, I would like to use the Atari with an old television with only RF input, therefore I need to fix the RF signal circuit.

 

I have access to some electrical tools (oscilloscope, soldering stuff, multimeter, …) but I would need some advice, where to start analysing the issue.

 

Are similar issues known or do you have advice what to check and how to proceed?

 

Thank you very much!

Edited April 8, 2020 by ranger81

[Voxel]

Have a good read:

 

[ranger81]

Hi Voxel,

I did read the mentioned topic, however the Jr. does not have the mentioned caps, voltage regulator was already changed by me without any effect. Also the 500k color adjustment pot was replaced with a new one.

My picture looks way more "snowy" than the picture of the other thread. I have 95% only static and 5% static that is different if I turn off the Atari.

I would be probably happy with the "light snow" on the other thread

Edited April 9, 2020 by ranger81

[Voxel]

Here:

https://mortoffgames.com/files/Atari_2600_Jr._Capacitor_Replacement_Kit_Installation_Guide.pdf?1113778879

 

You sound like you should know enough to read off the values from the caps in your Jr, and head off to somewhere like ebay and order replacements.

 

Whilst you're at it you may want to try a different lead in case its' the cause, causing a short.

[ApolloBoy]

There’s a tuning coil towards the lower right corner of the motherboard you can adjust (the red one), this coil allows you to change the RF tuning in case the picture quality is off. You’ll need a small Allen wrench to adjust it, ideally a plastic one since a metal one can throw off the tuning as you’re adjusting it.