ViewSonic A90f+-1 VCDTS23307-2R Service Manual page 18

H. freq.
FH < 32kHz
32kHz < FH
36kHz < FH
40kHz < FH
45kHz < FH
49.5kHz < FH
58kHz < FH
65kHz < FH
70kHz < FH
Pin 36 (F/V) provides horizontal C linearity control.
Pin 40 provide rotation signal to rotation circuit build by Q471, Q472 and Q473 and thus control the
current circulate the coil around the deflection yoke to rotate the display.
Pin 31 short to ground via 15pin D sub connector when it connect to PC. When it is not shorted to
ground, power saving feature is switch off, monitor will display "PLEASE CHECK SIGNAL" as self test
pattern. IA02 is E
6- 3 TIMEBASE CIRCUIT
6-3-1 TIMEBASE CONTROL (I301), HORIZONTAL
2
I301 is an I C control Time-base processor. By I
IA01(MCU).
H. sync, and V. sync. come from pin41, 42 of IA01 to pin1, and 2 of I301. When the H. Freq. is over 89
kHz or below 28 kHz, I301 will shut down to protect the horizontal output CKT from being damaged. The
horizon. Oscillator is built by C303 and R301, and determines the horizontal frequency range. C304,
C305, R302 build up PLL 1 loop filter.
Via Icon, the IIC-bus allows a linear adjustment of the relative phase between horizontal Sync.
and oscillator saw-tooth (in PLL 1 loop).
By and
between oscillator saw-tooth and horizontal. fly back (in loop PLL2)
The PLL2 phase detector is similar to PLL 1 detector, it compares the Horizontal. Flyback pulse at pin 12
with the oscillator saw-tooth wave-form. The controlled currents are independent of Horizontal. Freq.
The PLL 2 thus compensates for the delay in the output horizontal deflection CKT by adjusting the phase
of the HDRV (pin26) output pulse.
ViewSonic Corporation
IA01 o/p Pin20 Pin19
Cs0 Cs1
H
36kHz
H
40kHz
L
45kHz
H
49.5kHz
L
58kHz
L
65kHz
H
70kHz
L
87kHz
H
2
PROM for IA01 to save settings of all modes and DDC data.
, correction of pin unbalance and parallelogram are done by modulating the phase
Pin18 Pin17
Cs2 Cs3
H H H
L H H
H L H
H H L
H H L
L H L
H L L
H L L
L L L
2
C bus (pin29,30 (SDA,SCL)) it can communicate with
15
Confidential – Do Not Copy
A90f+-1