UPDATE:

One more round of pokey-fingers solved the problem. This time on the left side (when viewing the unit from behind) of the display IC.  I've done the same before, but this time it worked.  Perhaps due to my sweaty fingers this time?

Keith:

Yes, I did the Lexicon "shock test" and lots of finger poking and prodding.

I definitely don't have the tools for reworking any type of surface mount equipment, so I don't even try!  I think I'll stick with through-hole stuff.

Unless it gets any worse, I'll survive.  If I do get truly desperate, I'll track down a new one and pay the extortionate $200.

Ian

I would say 5.04 is within spec., did you get this voltage with an oscilloscope? But the problem though most likely on the display board, does not mean for sure it is. It is not uncommon for a processor solder joint pin to go bad, or be flaky. Did you try the Lexicon shock test? Sometimes just poking around the board and components with a finger will tell you if it's a bad solder joint.

You do need to have proper tools to work on surface mount boards. I use a $1500 lighted stereoscopic scope to see what I'm doing and use a top of the line $1200 metcal solder station to work on them. If you don't have right tools you can do more damage than good.

Keith:

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:

Futaba M202SD01HA

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...

It can never hurt to re-flow solder. Just watch the heat on IC's.

Well, I guess I won't be re-seating the display driver IC as it's surface-mounted.  Turns out the display is an integrated 3rd party VFD with a driver, display and controller built-in.  According to the manual for the display (Futaba), a control voltage (+5VDC) that's too high or low can cause errant pixel illumination.  Guess I'll have to measure when I get the time.

All:

My PCM 80 - which otherwise works like a champ - has recently started displaying errant pixels on its display.  It seems to be an actual pattern as opposed to random pixels.  Anyone ever seen this?  Clearing memory didn't seem to help.  I might try re-seating the display driver chip (I'm making the assumption that this is possible, as I've never been inside one before), but I don't have any ideas other than that...