Sony 17SFII monitor missing green color

Monitor: Sony Multiscan 17SFII

The problem came a while ago as a sudden when the screen showed more
pink color and less brightness. Kicking the monitor and trying
adjustment buttons from the front panel doesn't help. I took out the
monitor's signal cable and measured the resistance for each pins and
it seems the cable is just OK.

Next I used a good monitor to draw Red, Green and Blue three colors
and then swap to this Sony monitor. I can see the spot where is
supposed to be GREEN color but just show a complete dark area. So the
problem with the monitor is missing Green color.

I tried to peek and remove the circuit board attached to the neck of
the CRT but there is a metal shield soldered to the this circuit
board. Did not use a hammer to disarm this, though. How can I safely
remove it so I can check for any loose soldered joint/ fault points?
What should I test next. I will appreciate someone can show the
detailed experience. Some articles have mentioned that the failure of
one gun is highly rare and I will suspect the problem is on the board.

Also, There are some high voltage caps inside. I can easily see one
pasted to CRT 'belly' with fat red wire attached. Where is the another
one located? (on the chasis circrit board?).

 

Before you do anything else make SURE the green gun is ok,. yes a
marginal cathode emitter can rapidly fail. Turn up the screen control
(on the flyback) and see if there's any green, maybe turn down the red
and blue bias controls. Even a failed driver transistor will allow
the green to be turned up enough to see something, although it'll have
retrace lines. Occasionally a shorted spark gap or open transistor
will completely kill one gun so try swapping the green wire to the
tube with one of the other colours.

. Steve .

 

On the CRT neck board, there is a large IC that contains the driver transistors
to drive the picture tube. Sometimes, one of the three video channels will
go bad. You can download a data sheet on the IC from the web.
Measure the voltages on the video input and output lines of the IC.
If one color is way different from the other, the IC is probably bad.
You should also scope the video inputs on the IC to make sure that
they are all present.
John