Sony BVM-D32E1WA Maintenance Manual page 97

Beam current correction signal
When the average beam current changes, the constituent parts inside the CRT receive the thermal change
that results in a slow change of the beam landing condition. The correction waveform that corrects the
landing change, is created using the integration characteristics of the resistors and capacitors as shown.
A
Amount of change
of beam landing
Amount of change of beam landing after the main power of the monitor is turned on
The ABL signal that corresponds to the beam current, is inputted from IC805 pin-1 to the point "A" in the
illustration. The integrated voltage of the ABL signal appears at the points "B" and "C". These voltages
are buffered by the voltage followers A1 and A2, and are mixed and inverted by A3. In this circuit the
resistor R1 and the capacitor C1 provide the longer time constant while R2 and C2 provide the shorter
time constant so that the slower curve and the steeper curve are mixed in order to resemble with the
amount of change of the beam landing. The output at point "D" is added to the LCC drive.
In the actual circuit, the two separate circuit systems are prepared to resemble with the amount of change
of the beam landing. Outputs from IC606 pin-1 and pn-7 generates the waveforms that resemble with the
amount of change of the beam landing at the four corners.
LCC drive block
The respective correction signals are added and inverted by IC620, IC621 and IC622 (1/2) for respective
five coils. These signals are outputted to the optional amplifiers IC700, IC701 and IC702 via switches
IC623 and IC624, which drive the respective correction coils.
BVM-D32E1WA/D32E1WE/D32E1WU
B
A1
R1
C1
C
A2
R2
C2
When the reference beam current flows
A3
D
When the beam current
is small
Time
When the beam current
is large
6-9