Submitted October 2026

     Since repairing my PET (twice!) I have been going through and playing a variety of games on it. Amazing what the community had done with a computer that was designed for text!
Then I started to notice something... small 1 pixel line "artifacts" on everything that used the PETSCII graphics. At first I thought this was another fault but upon researching this I found others over the years have noticed it as well. It seems that everyone had just accepted it as normal for the PET (at least this revision, not certain about others) and nothing was ever done about it.
     Look at the photos; these are the lines. This is just the Queen card in Blackjack, but they were on every game I tried. So I decided to try to do something about it. People have reported those lines over the years, but they seem to have been accepted as a normal PET quirk. Re-timing the signal shows that they can be cleaned up without changing the graphics or resolution. My sub-board was designed and tested for the 320351 motherboard.
     The artifact is not really evident until you play games and the screen is full of graphics. There are so many new game programs and demos on this machine now that the artifact became really evident across everything I was loading. It's always been there but I guess many never knew it as they were just using the machine for text applications and it doesn't reveal itself there. But a few people did notice it over the years but nobody ever came forward with a solution.
     The real breakthrough was when I tested a modern clone PET motherboard and that did NOT exhibit the artifact. Then I spoke to someone who created a clone board and I saw how he was accomplishing the clean video and applied it to the original machine. This was the first thing I ever actually designed and I am super happy it works (and I have a PCB with my name on it on my PET now too...lol!)
     The "PET Video Cleaner" as I have dubbed it uses a 74LS74 flip-flop and the PET’s 8 MHz clock to clean up the timing of the video signal before it reaches the monitor. This suppresses brief glitches that appear as faint vertical lines or seams between characters.
     I just received the boards today from PCBWay and built one up to test. I designed it to be a drop-in replacement for UG11 (72LS20). Just pull LS20, insert into the PET cleaner, install a 74LS74 in the second socket, and install it into the socket where the LS20 was. A jumper wire goes from the board to PIN 2 of UE11 to grab the clock signal. Designed to be totally reversible, however LS20 is originally soldered to the board so that did need to be removed and socketed in the first place. And the pictures speak for themselves. It works and no more lines!

     Here is a link about it that I found and helped lead me to the direction to fix it:
https://forum.vcfed.org/index.php?threads/strange-video-effect-on-some-characters-pet-2001-n-board.1239511/

Info on how to make your own: https://github.com/eightbit0675/PET-Video-Cleaner/tree/main

Bruce Charles Philip aka eightbit <brucecharlesphilip@gmail.com>