I've noticed on my two 2600's, there is a vertical blue line displayed at what appears to be the edge of the drawing field. I had never noticed this line on any of my other 2600 compatible systems, and never owned a true (working) 2600 until recently. I tried searching for anyone else mentioing this, but couldn't really find anyone reporting a similar issue.
Long story short, I grew up playing 2600 games on my Colecovision with the expansion module. Around 16-17 years ago, I also picked up a pair of 7800's and a system changer for my Intv2 that I occasionally played 2600 games on. I never had a true 2600 until about 8 or 9 years ago someone picked up a 4 switch for me at a yard sale. But the power switch was broken, so I never used it. This past spring, I found an original channel 3 only heavy sixer for a good price at the Midwest Gaming Classic, so I bought it. I decided to repair/refurbish both of them, so I ordered a new power switch for the 4 switch, and two cap/refurbish kits. The 2600's work perfectly, with the exception of the blue vertical line.
The line is very evident on the 4 switch (rev 13). Here is a shot of Moon Patrol, which shows an offset blue line. The top line is where the aliens stop flying to the left. Which makes me think that it is drawing it at the edge of the field, and moon patrol's title screen has two separate drawing fields.
On E.T., the line is perfectly straight all the way up.
On the H6, the line is there, but not nearly as noticeable.
On my 7800, the line is non existent. Same goes for my Coleco expansion module and my Intv2 System Changer. This picture is from the 7800, I didn't take pictures of the other two.
I also noticed it on my Harmony cartridge, that the blue line shifts depending on if there is text on the line or if it's a blank line in the game list. All screen shots above were using my actual Moon Patrol and E.T. cartridges, so it is not an issue limited to just the Harmony either.
Is this being caused by a part that is failing or falling out of spec? The fact that only the 2600's are exhibiting the issue and not the clones or the 7800 makes me think it's something specific to the 2600's circuit design. All systems are stock (ie, no A/V mods) except for the caps that have been replaced (the e-caps, the usual suspect caps, and the voltage regulator) and I am using the RF out to send the signal straight into the antenna coax (using a length of RG6 quad shield I made up).
Has anyone else seen this issue? Any input is greatly appreciated.