Horizontal Width Control Circuit; Horizontal Drive Circuit - Mitsubishi Diamond Plus 93SB Service Manual

3.2.3 Horizontal Width Control Circuit

Q314 is controlled by the horizontal drive pulses from IC501. While Q314 is turned ON, the energy is stored
in the horizontal deflection yoke. When it is turned OFF, the stored energy flows into C331 and C332. This
operation is repeated to maintain the horizontal deflection. The voltage of collector pulses at Q314 is divided
by C331 and C332, and the resultant pulses are used for the switching synchronization of the high voltage
control IC301 and the generation of horizontal blanking pulses. The horizontal width is controlled by
changing the B+ drive pulse duty of the output at IC501 Pin 6. When the duty is changes, the rectifying
voltage of D317 and the "S" correction capacitor changes. Then, the horizontal width also changes. The
vertical parabolic waveform is generated within IC501 and the resultant output is generated at IC501 pin 5.
This output is then applied to the B+ drive pulse generator circuit through R512. By virtue of this parabolic
output, the correction control can be conducted for the pincushion, barrel trapezoidal and upper/lower
distortions.

3.2.4 Horizontal Drive Circuit

In the horizontal drive circuit, the horizontal oscillation drive pulses output from IC501 (TDA4856) pin 8
H_DRV of the oscillator are used to convert the power supply of 26V to the base drive current fed to the
horizontal transistor through the drive transformer T304 and the switching FET Q313.
26V
H_DRIVE
(From U501 8pin)
(Fig. 3.2.4) Horizontal Drive Circuit
7-9
Horizontal transistor Q314
Base current Ib