ViewSonic P90F Service Manual download pdf (Page 19)

When the sync signals are both exist, then IA01 will send Low at pin 13 to switch on the relay

BR801 via Q104 and Q104A and thus produce a very high current circulate the degaussing coil

and this signal will sustain for a certain period. Thus the display is demagnetized

The sync signals are buffered by IA01 and output at pin 41, 42 to synchronize the timebase

controller I301. IA01 will also initiate I301 by IIC bus build by pin 28(C.SCL), pin 27(C.SDA).

This IIC bus is also responsible to initiate the video pre-amplifier I901and OSD I903. After the

initiation is completed I301, I901 and I903 will operate normally. This IIC bus also provides

Purity control, through P421, connect to PWB-0417, purity control board.

Pin 17 to pin 20 and pin32 provide the logic to control the horizontal CS linear correction circuit

according to the horizontal frequency range as the following table.

P90f CS Table

CS4 CS3 CS2 CS1 CS0

MCU Pin 32 17 18 19 20

Capacitor C425 C421 C420 C419 C423

Hf <32KHz H H H H H

32KHz<Hf<=36KHz H H L H L

36KHz<Hf<=40KHz H H L L L

40KHz<Hf<=45KHz L H H H H

45KHz<Hf<=52KHz L L H L H

52KHz<Hf<=58KHz L L H L L

58KHz<Hf<=65KHz L H L H H

65KHz<Hf<=70KHz L L L H L

70KHz<Hf<=86KHz L H L L H

86KHz<Hf<=96KHz L H L L L

Hf>96KHz L L L L L

Pin 36 (F/V) provides horizontal C linearity control.

Pin 40 provide rotation PWM to rotation circuit build by Q701, Q702 and Q703 and thus control

the current circulate the coil around the deflection yoke to rotate the display.

Pin 1 provide Horizontal convergence control through Q426,Q427, Q428.

Pin39 provide Vertical convergence control through Q305, Q306, Q307.

Pin 31 short to ground via 15pin D sub connector when it connect to PC. When it is

disconnected, power saving feature is switch off, monitor will display “NO SIGNAL” as self test

pattern.

IA02 is E

PROM for IA01 to save settings of all modes and DDC data.

8-3 TIMEBASE CIRCUIT

8-3-1 TIMEBASE CONTROL (I301), HORIZONTAL

I301 is an IIC control Time-base processor, By IIC bus pin30, 31(SDA,SCL) it can communicate

with IA01(MCU)

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P90f-1

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ViewSonic P90F Service Manual Page 19