25 Sep
2008
25 Sep
'08
11:24 a.m.
The thing I've learned is that the controls usually interact - so if
you don't do things in the 'right' sequence, you can wander so far away
from 'good' settings that you'll never get back. Or so I've heard.
;-) -- Ian
They do, and HP docuemnt the fact.
There are basically 7 adjustments -- gain and cutoff for the 3 video
amplifiers and the 1st anode voltage ('screen grid' across the Pond, in
the UK we call everything after the cathode and control grid an 'anode',
in the States, you have the cathode, several grids and one (final)
anode).
I can't remember the exact procedure, but it's basically to determine the
cut-off voltagees for the 3 electron guns, set the A1 voltage so that lowest
cut-off gun is just on the point of cut-off, then for each electron gun to
determine the cut-off voltage for a totally black (level 0) and just on
(level 1) raster, and set the cutt-off preset to the average of those 2.
Then display a level 15 raster, adjust the gain for right intensity, and
then repeat the cuttoff and gain adjustments for that amplifier because
they interact. And then do it for the other 2 amplifiers.
Perhaps I should explain that there are 3 4-bit DACs inside the computer,
one for each primary colour and that a 'level n' raster is when <n> is
fed to that DAC for the entire screen.
-tony