There is an IC that implement the power switch toggle effect. That is
where
the problem lies. The front panel power switch is connected to the clock
input of this flip flop via some RC network but for some reason it doesn't
want to flip. If I manually connect the +12V to the set or reset pin of
this
flip flop, I can turn the monitor on / off at will. So I can add a toggle
switch to do this; it would just look a little ugly.

So you are talking about IC30, the MC14013B dual D-type flip-flop?

You're a walking IC encyclopedia?

AFAICT, the circuit looks like this:

|----------------------|
| |
| |-- R -- Vcc |
| | |
| ____o___ |
Vcc | | S | |
| | | | |
R |---| D Q*|-- R94 --+
| | | +_|_ C11
+----+---|Clk Q |-- ___ 10uF 16V
| _|_ | | on/off |
/ SW ___ |___R____| |
| | C o _|_
_|_ _|_ | =
= = |--- R --- Vcc

R94 and C11 effectively debounce the switch. If the chip is OK, then
I'd suspect that C11 is open. Try connecting a 10uF cap in parallel
with C11.

Close enough. I tried assuming each of the component is bad and did a patch
test (e.g. short the cap to Vcc or to gnd) but still couldn't make it work.
I hooked up a scope on the Clk and it shows a pulse when the power switch is
pressed. If I use a frayed wire to short the switch (this creates many
pulses) then it sometimes work after many attempts. Increasing or decreasing
the voltage by 1.5V doesn't help (use an ohmeter Rx1 range to short the
switch).

I don't know if it's a good idea to try to replace this chip. It's surface
mount and the chip is small (about 1cm) and the leads are even smaller.

I'll play with this until I get tired of it. If I can not figure out the
definite cause then I'll just glue on an additional switch.

I hope other LCD manufacturers are as nice as viewsonic in providing
circuit
diagram. Has anyone ever obtained repair manual for other brand of LCD
monitors?

Mitsubishi Electric Australia will sell me a manual for mine, without
an NDA. LG supply manuals for their LCD TVs, without an NDA. The FCC
database has many circuits for LG monitors and other manufacturers,
all of which you can download ... without an NDA.

Thanks for the info. I didn't know FCC has circuits in their database.