![background image](http://html1.mh-extra.com/html/viewsonic/a90f-1/a90f-1_service-manual_1020116018.webp)
IA01 o/p
H. freq.
Pin20
Cs0
Pin19
Cs1
Pin18
Cs2
Pin17
Cs3
FH < 32kHz
H H H H
32kHz < FH
d
36kHz
H L H H
36kHz < FH
d
40kHz
L H L H
40kHz < FH
d
45kHz
H H H L
45kHz < FH
d
49.5kHz
L H H L
49.5kHz < FH
d
58kHz
L L H L
58kHz < FH
d
65kHz
H H L L
65kHz < FH
d
70kHz
L H L L
70kHz < FH
d
87kHz
H L L L
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
2
PROM for IA01 to save settings of all modes and DDC data.
6- 3 TIMEBASE CIRCUIT
6-3-1 TIMEBASE CONTROL (I301), HORIZONTAL
I301 is an I
2
C control Time-base processor. By I
2
C bus (pin29,30 (SDA,SCL)) it can communicate with
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 , correction of pin unbalance and parallelogram are done by modulating the phase
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
15
Confidential – Do Not Copy
A
9
0f+-1
Summary of Contents for A90f+ 1
Page 57: ...12 PCB Layout ViewSonic Corporation 54 Confidential Do Not Copy A90f 1...
Page 58: ...VIDEO PWB 0414 ViewSonic Corporation 55 Confidential Do Not Copy A90f 1...
Page 59: ...KEY CONTROL PWB 0488 ViewSonic Corporation 56 Confidential Do Not Copy A90f 1...
Page 60: ...MAIN BOARD 13 Schematic Diagrams ViewSonic Corporation 57 Confidential Do Not Copy A90f 1...
Page 61: ...VIDEO ViewSonic Corporation 58 Confidential Do Not Copy A90f 1...
Page 62: ...KEY CORTROL ViewSonic Corporation 59 Confidential Do Not Copy A90f 1...
Page 63: ...POWER SUPPLY CKT ViewSonic Corporation 60 Confidential Do Not Copy A90f 1...
Page 64: ...MCU CONTROL CKT ViewSonic Corporation 61 Confidential Do Not Copy A90f 1...
Page 65: ...Time Base DeflectionCKT ViewSonic Corporation 62 Confidential Do Not Copy A90f 1...
Page 66: ...H V DYNAMIC FOCUS CKT ViewSonic Corporation 63 Confidential Do Not Copy A90f 1...
Page 67: ...14 Exploded Diagram ViewSonic Corporation 64 Confidential Do Not Copy A90f 1...