🚀 go-pugleaf

  > recently we've been having problems with one of our Sun 3/50's. A Sun (?)
>technician while here fulfilling a service contract on a different machine
>was asked why the screen blinks/flickers. He said that the problem is
>static electricity -- it builds up and when it discharges the screen blanks


Two possibilities come to mind; unfortunately, only one gives you any hope
of any easy fix.

Assuming that by "blinks/flickers", you mean that the video simply "goes
away" for a short period of time, there may be a break somewhere in the
video signal path.  Look for a defective cable or connector between the
monitor and its driver, or (less likely) there may be an intermittent
contact - such as a tiny PC trace cracking - on the video amplifier board
itself, or between the video amp and the CRT base (the CRT connector).

The other possibility is a common one with CRT displays, particularly ones
which are fairly new or have been recently subjected to some sort of 
mechanical shock.  This is "flashover", and it's what I suspect the tech
was actually referring to.  It's not really caused by "static"; in flashover,
a defect in the structure of the electron gun, or some small bits of debris
within the tube, can provide points for momentary high-voltage arcs within
the tube.  This may be accompanied by a "snapping" sound as the tubes blanks,
and/or visible arcing in the neck of the CRT.  If it's a gun defect, the only
solution is to replace the CRT.  If it's debris, the offending particle is
often "burned out" by the arc.  Debris particles are always present to some
extent when the tube is new, or may be "knocked loose" (phosphor flakes, etc.)
if the unit is jolted.  In either case, they will usually work their way
back to the neck and be burned out over a few days or so of normal use.  If
the problem persists longer than a week, with no sign of decreasing
frequency, you should assume that the tube is bad and is in need of 
replacement.


Bob Myers  KC0EW   HP Graphics Tech. Div.|  Opinions expressed here are not
                   Ft. Collins, Colorado |  those of my employer or any other
{the known universe}!hplabs!hpfcla!myers |  sentient life-form on this planet.