and VD408 (9.1V) for voltage regulation and is then sent to Pin 12 of TMPA8899-XXXX
as the feedback pulse of the horizontal AFC pulse. The pulse output by Pin 10 of T471 is
rectified by VD447 and filtered by C447 to 180V voltage, which is supplied to the
transmittal circuit as supply voltage. Pin 9 is kinescope electron beam circulating pin, i.e.
automatic brightness limit (ABL) pin, which supplies to Pin 27 of TMPA8899-XXXX for
automatic adjustment limit of screen brightness.
6. Scanning circuit:
Field output stage circuit mainly consists of N451 integrated circuit and its peripheral
circuit. After synchronous separation, field synchronous signal is sent to field saw wave
formation circuit via field frequency dividing circuit; then field saw wave actuating signal
is output from Pin 16 of TMPA8873-XXXX, sent to Pin 1 of N451 via R451, and output
from Pin 5 after internal actuating amplification and output power amplification, and
passes a field deflecting coil; vertical saw current flow through C457 and R459. C450,
R454, R453 and R461A/B are field feedback elements setup mainly in order to improve
field linearity and stabilize field circuit working points, and the field feedback signal is
sent to Pin 7 of LA7841. VD451 and C451 form a self voltage booster circuit, so that the
supply voltage of Pin 6 of N451 is 32V during forward field scanning period and is
boosted to 48V during backward field scanning period, so that the working efficiency of
field output stage is improved, and the supply voltage of Pin 7 during the backward field
scanning period is lower than the amplitude of field backward pulse of Pin 5, effectively
removing the backward retrace line. In addition, when the screen scanning is of poor
linearity, the fault usually occurs at the self voltage booster circuit.
7. Primary color exciting circuit:
The task of the primary color exciting circuit is to excite and amplify three primary color
signal and output RGB signal of around 130Vp-p and modulate RGB electron beam
current of the kinescope. Primary color exciting circuit usually includes white balance
adjustment function, which is mainly completed by I
2
C bus control.
RGB primary color signals are on V901, V911 and V921 base electrodes respectively and
amplified by the common emitter of the three tubes, and output by the collector and
directly coupled to V902, V912 and V922 for common base amplification. The
