Tektronix 212 Instruction Manual page 32

Circuit Description - 212
CRT Circuit
The CRT circuit provides the high voltage and control
circuits necessary for operation of the cathode-ray tube
(CRT ) . Figure 6-5 shows a detailed block diagram of the
CRT circuit. A schematic of this circuit is given on diagram
3.
Rectifiers CR261 through CR268 provide the negative
accelerating potential for the CRT . Voltage output is
6-6
FROM
POWER
SUPPLY
CIRCUIT
REFERENCE
CURRENT
To U105
HIGH
VOLTAGE
SUPPLY
FOCUS
R398
approximately -1000 volts at the CRT cathode . Filament
voltage for the CRT is provided by a spearate winding of
the power transformer . Display intensity and focus are
controlled by R395 and R398 respectively . The Trace
Rotation adjustment controls the current through L300
and affects both the vertical and horizontal alignment of
the CRT beam .
INTENSITY
R395
L300
V300
Fig. 6-5. CRT Circuit detailed block diagram .
R144
R145
UNBLANKING
SIGNAL
FROM
Q134
R141
TRACE
ROTATION
A1