Sony TRINITRON PVM-14L2 Service Manual page 52

2. CXA1739S peripheral circuit
IC231 (CXA1739S) accepts the Y/Cb/Cr signal from 1. -(2) at pin-1 (Cr), pin-2 (Cb) and pin-3 (Y). It
also accepts the RGB signal from 1. -(4) at pin-10 (R), pin-11 (G) and pin-12 (B). Either one of these two
input signals is selected inside the IC. This IC contains the function of applying the matrix processing to
these signals and to generate the CRT drive output signals.
At the same time, this IC contains the automatic cut-off control function that is used to apply the current
feedback to the CRT drive.
3. ABL circuit
The ABL circuit consists of the PIC ABL circuit that is Q239 and the BRT ABL circuit that is Q235. The
emitter circuit of these two transistors receives the ABL voltage that is supplied from the deflection block
while the base circuit of these two transistors receives the DC voltage that is generated by dividing +12 V
power voltage. The collector circuits of two transistors are connected to IC231 pin-46 (PIC control) and
pin-7 (BRT control) respectively. When the transistors Q239/Q235 are turned on, their control voltages
decrease to activate the ABL operation. The different base circuit voltages are switched between the 16:9
aspect mode and 4:3 aspect mode by Q242 so that the ABL operations are also switched.
4. Blanking pulse shaping
The H blanking pulse is generated by IC356 and IC357 from the AFC pulse supplied from the G board.
Duration of the H blanking signal is changed by changing the pulse width using IC356. The V blanking
pulse is generated by IC353 and IC355 from the OR-gate output between the V SYNC (pin-4) pulse from
IC104 and the V deflection pulse from the G board. Duration of the V blanking signal is changed by
changing the pulse width using IC355.
5. BLUE ONLY circuit
When the BLUE ONLY button on the front panel is pressed, this signal is detected by IC451 (CPU) and
sets the B/O line to low. This signal is again detected by IC232 that mutes the green/red signals that are
output from IC231. Note that the signal is not muted during the V blanking period because the lk refer-
ence pulse that is used for automatic cutoff circuit, is super-imposed in the V blanking period.
6. AUTO CHROMA PHASE
When the specified color bar signal is input, the R, G and B signal levels that are output from IC231 are
detected by Q245, Q244 and Q243, and are input to pin-74, -75 and -76 of IC451 (CPU). The AUTO
CHROMA PHASE circuit functions to that the above signal levels match with the reference level with
the use of SUB CHROMA/SUB PHASE.
7. System control
This apparatus is controlled by IC451 (system control CPU). Various settings are saved in IC450 (EE-
PROM).
8. Parallel remote control
Statuses of the parallel remote terminal are read by IC3770 of t he Q board, transferred to IC451 (CPU) to
control this apparatus.
5-2
PVM-14L2/20L2