2600 Jr with tfw8b deluxe AV Mod: Black and White image

[root42]

So I have this Jr, the version without the RF can, PAL. I followed these instructions and removed the 8 components (plus RCA jack) and installed the mod. 
 

Sound works, picture works and is SHARP. But it is only black and white, no matter which cartridge I try! Toggling the BW switch doesn‘t help either. 
 

What issue might I have? I have a scope and can probe around, but I am not sure what I should probe. I guess I start with Pin 9 of the TIA, which is Color?

 

[root42]

Probed Pin 9 of the TIA: it’s looking good. 
 

 

[root42]

And the red and yellow cable show these waveforms:

 

 

[root42]

Well, all waveforms looked good. So I tried again…

 

and it works! Why? What did I do?

[+Stephen Moss]

Sounds like you might have a bad solder joint somewhere and that probing and moving the PCB has resulting in a better connection (for now).

[root42]

9 hours ago, Stephen Moss said:

Sounds like you might have a bad solder joint somewhere and that probing and moving the PCB has resulting in a better connection (for now).

Yes, that might be it. Well, the case is currently closed. So if it happens again, I will open it up and reflow all joints in the signal path.

Now that it's working I must say: the mod worked brilliantly! Extremely sharp and noise-free output! I am very happy. Much better than the mod I did for my Vader, using parts I had lying around.

 

Edit: Also I reflowed the AV mod cables, so maybe that already did the trick.

Edited May 19, 2021 by root42