I own and have repaired some ADM-3A terminals, and I have electronics experience from the era. I did not see the posted image, from the VCF Web archive of messages. I just walked through the ADM-3A Maintenance Manual, which is on Web online archives. I did not see any "invert video" DIP switch setting. I did not see any description about how to invert video. And - at a glance - I did not see anything on the schematic on the logic board, which suggested a simple means to invert video. Of course I may have missed something; or my manual may not match the actual terminal. But I'm confirming the owner's impression that there's not likely a "toggle switch" in play. I'm afraid, the apparent inverted video, may be a real issue and not just some inadvertent setting. So: it's either a deliberate "mod" for purpose, or some logic failure. I doubt it's a monitor failure - that can be diagnosed, by using an oscilloscope to look at the incoming CRT monitor signal, to see if it is standard NTSC type video. This calls for technical experience and use of an oscilloscope. An oscilloscope will show actual signals. If there is a mod, jumper or failure, "walking through" with schematic and oscilloscope will find it. The logic board should be inspected for any wiring modifications. The board can be removed and decabled for such inspections. Be VERY CAREFUL because 1) various pieces of insulating "cardboard" are EXTREMELY fragile, 2) there's risk of shock from the 15,000 volts on the CRT - a charge that the "tube" retains after power-off, and 3) of course any physical issues from handing old electronics, boards, cabinets. Standard disclaimer: I'm not responsible for loss, injury or damage. Use any information I provide at your own risk. I may be wrong, confirm anything I've suggested. Herb Johnson -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT retrotechnology DOT info