Rolling interference bar on restored PAL Light Sixer - advice sought

HEXdidnt · November 11, 2022

Earlier this year, my folks dredged up our old Atari 2600 during a tidying session in their loft, boxed, but partially disassembled. Last I remembered using it (late 70s/early 80s), it didn't work at all, so imagine my surprise when we put it all back together and got not just a picture out of it, but functional, playable games.

However, the picture included a rolling bar of interference and whiteout, moving from the bottom of the screen to the top:

I was advised to replace all the capacitors, the power regulator and a decidedly dodgy-looking PSU (Ingersoll-branded, and barely held together by what little tension remained in the fossilised sellotape wrapped around it!). Alongside that, I figured I may as well do the Composite Video mod for a slightly sharper picture, and greater ease of attaching it to modern TVs. Initially, the results were excellent, and revisiting the machine that introduced me to videogames was a pretty thrilling experience - so many great memories, and it opened up the possibility of acquiring games I'd missed out on back in the day.

However, after a while there appeared a rolling bar of interference moving, as before, from bottom to top. Initially nowhere near as bad as when we first tried the machine after its 40+ years in the loft, but it's definitely there... and it seems to be slowly getting worse over time:

I had a friend give the machine a quick once-over with an oscilloscope, and there's definitely some noise on the video output. The conclusion he reached was that it's "a grounding issue", but that there's no clear solution. One idea was that the replacement PSU I acquired was of the cheapo-cheapo variety (guilty as charged - the first one I bought pretty much exploded within a week of receiving it, but the replacement has lasted well so far) and that I might be better off with a higher quality model.

Does anyone here happen to have experienced anything similar? Any recommended fixes (I'm reasonably good with a soldering iron now!), or specific PSUs to replace the one I have?

Also wondering if, perhaps, looking into S-Video output might be a worthwhile project in future...

Edited November 11, 2022 by HEXdidnt

HEXdidnt · March 16

Curious update to this issue. Last time I took the 2600 along to the Computer Club, I plugged it into a CRT rather than an LCD screen, and the picture was flawless. Didn't even develop the rolling bar of fuzz after extended use.