pc7300 monitor problem (summary report)

[randolph.little]

Thanks for your insight regarding the impending failure of the monitor
on my pc7300 "bonasa" which was experiencing compression of characters
toward the right edge of the display and leftward drift of the entire
page so that column 1 was hard to view behind the bezel.  Here is a 
summary of events, discoveries and actions:
1) All seemed well for five virtually continuous years of operation.
After logging off I always turned the brightness all the way down so
as not to burn the login pattern into the crt, but otherwise bonasa
was left powered up all the time.
2) About a month ago signs of horizontal nonlinearity began to appear,
as the rightmost characters started shrinking day by day; and about a
week ago column 1 had shifted far enough leftward to become a concern.
3) Yesterday we took the back off of the monitor and determined that
the horizontal phase adjustment would affect the centering of the
raster, but that it was already so close to the end that column 1
couldn't effectively be brought into better view -- nor did it affect
the linearity.  The monitor layout matched that described by Harry
Maddox in Rob Stampfli's recent article, and C411 looked somewhat
bloated, so I suspect it was the culprit.  BTW, the monitor on my own
personal 2x40 pc7300 has a later (ie, 1986 rather than 1985) layout
which doesn't have a C411 equipped, even though there is such a
designation stencilled on the pwb in an area of unequipped compenents.
4) Since our local corporate data system support people were able to
locate a spare monitor, we decided to swap monitors today rather than
attempt to replace C411.  So last night I logged out and turned down
the brightness as usual.
5) This morning when I turned the brightness control back up, guess
what?  That's right, no raster!  So it is certainly time to replace
the monitor.
6) The replacement is a 1986 model, on a high-rise 3B1 pedestal.  Its
circuit layout matches that on my own machine rather than the original
monitor on bonasa.  Unfortunately, the 3B1 top doesn't readily replace
the pc7300 top because the front pair of attachment points are screw
posts on the 3B1 but latch posts on the pc7300 base, and the flexible
ground contact strip on the 3B1 pedestal doesn't properly reach down
far enough to make good contact with the pc7300 half-height disk case.
7) After a couple of hours of tedious disassembly and reassembly, the
monitor from the newer 3B1 pedestal was remounted onto the old pc7300
pedestal.  Were bonasa my own personal machine, I would have tried to
adapt the 3B1 pedestal to the pc7300 base, in case I ever wanted to
put a full-height hard disk in to replace the 40M HH unit.
8) Now bonasa is back on the air and the screen looks like new, thank
you!  Wish I could have kept the old monitor to test C411 and to try
to repair, but it was taken back to the data system depot.
     Thanks again for your help.  Happy Thanksgiving!  -- Randy