The display in the PCM80/81 is a standalone, self-contained item that consists of the display controller, driver (all surface mount - I don't have the tools to comfortably reflow anything that small) and display all on a single daughter card. The daughter card connects to the mother board via a 20-pin IDC, which I've unplugged and reseated a few times. I tracked down the service manual for the display itself:
The manual contains a full instruction set for the display, including codes to send a full reset of all pixels. The manual also mentions that low or high 5V supplies can cause errant pixel dimming or illumination, respectively. My 5V rail measures 5.04V, which I figure is probably safely within spec. I suppose if I really wanted, I could pull the display out, power it up and send a reset function on my powered breadboard. I'm not sure I want to go that far, as I can still read my display and the ol' girl still works like a champ. And I would think that Lex engineers would send a full reset command to the display on startup anyway. But you know what they say about assumptions...