Tektronix 7834

zero
to
---5
Volts . The coupling of the 10 kilohertz Ramp
waveform
through C2718 and R2718 produces a 2
volt
ramp
at the Storage Mesh superimposed on the Variable
Persistence
Operating Level .
When Erase goes HI, Prep also goes HI turning 02714
on
and 02730 off .
Transistor 02755 also turns off momen-
tarily interrupting
the current flow through R2733 which
turns 02734
on
.
After the Erase pulse, 02734 is still on so
the voltage on the Storage Mesh is at the level set by R2725 .
As
C2753
discharges, the emitter of 02755 falls turning
off
02734 after
approximately 200 milliseconds . This causes
current to flow
through R2736 to raise the Storage Mesh
to
the Variable
Persistence Prep Level, adjusted by R2735
from zero
to 12 volts above the Operating Level . At the end
of the X pulse,
the Prep signal goes LO returning the de-
coder to its initial state .
In
the Fast Variable Persistence mcde, operation of
the
Storage Mesh Decoder is unchanged until the end of the X
pulse . In
this mode, however, the Y pulse follows the X
pulse holding
the Prep signal HI and the Storage Mesh at
the Prep Level for
another 400 milliseconds . In addition W
goes HI and remains HI until the end
of the Tsfr pulse and
Fast Prep oscillates at the Clock signal
frequency . These
Trace Alignment
Theory of Operation--7834
signals cause the Storage Mesh to drop to the Hold Level at
-35 Volts after the Y pulse and remain at that level until
the
Tsfr pulse occurs . Superimposed on the Hold Level are
the
"Pump
Pulses", logically inverted from the Fast Prep
signal and with height adjustable by R2705 from zero to
15 Volts above the Operating Level .
The'Trace Rotation supply, consisting of U2468A, 02468,
and 02469, is an operational amplifier providing
a low-
impedance adjustable voltage source for the trace rotation
coil . The TRACE ROTATION control R2465 determines
the amplifier's output voltage and therefore the current in
the coil
.
The Reduced Scan Trace Rotation adjustment,
R2470,
sets the difference in current required for the trace
rotation coil in the Reduced
Scan mode . Resistor R2470 is
activated only in the
Reduced Scan mode when +15 Volts
and --15 Volts are applied
to pins 9 and 10 of P2504
respectively .
The Y-Axis alignment supply, consisting of U2468B,
02478, and 02479, operates similarly to the Trace
Rota-
tion supply, except that the difference in current required
between Full
Scan and Reduced Scan modes is provided
by fixed resistors R2471
and R2472 .