On 9/22/2016 1:17 AM, Mattis Lind wrote:
I cannot find anything mentioned about character blanking in the circuit
I read this on the topic "Alphanumeric Display":
"Refer to the display control block diagram (Fig 6-13). The display
coordinate position is generated through the digital-to-analog converters
(X DAC and Y DAC) and fed through the filter circuitry with the filtering
disabled. A short time later, either SOT is activated to print a cursor
refresh dot or ADOT is activated to print a character dot. The timers for
cursor intensity and character intensity are adjustable by potentiometers
accessible through the bottom of the assembled instrument."
Maybe this is the "A short time later" that it is not working since seems
to draw instantly. But as far as In understand that timer is generated in
the digital parts.
Note that this is not a computer or terminal. It is an instrument per
Unfortunately the detailedness of the circuit description is not up to the
DEC standards in my opinion. There are no scope diagrams describing the
pulses going to the Z-axis as far as I can see which is unfortunate.
The beam is required to stay at one location for a certain time and
intensity to be stored in the CRT. If it's moved, or if the intensity is
too low, it will not be stored.
The cursor is set to a lower intensity so it can be seen on the CRT,
flashing, but will not store. Characters are brighter and left on long
enough to be stored. Only
the cursor is refreshed, the characters are stored once, then the beam
is moved to the next position.
It looks like something is moving the beam around when it shouldn't,
drawing on the screen.
Vintage computers and electronics