Not seeing red

[Rob Judd]

Hi,

The monitor I'm staring at right now was recently given to me by a
friend who upgraded to LCD. It's a KTX 17" CAG-664SG and has an unusual
problem; the red gun only works about half the time.

Now before asnyone states the obvious, I repaired monitors for about 12
months at one point and so I've tried all the usual things. The case is
off and tin cover removed from the neckboard, and no amount of
mechanical tapping or spray freeze affects when this fault decides to
show itself. I've also cleaned the plug onto the tube, and the one from
the VGA connector at the back going to the neck board.

The only thing consistent is that switching it off and back on will
almost always bring the red gun back, even if only for a minute or two.
It will also sometimes come back on by itself, and has been known to run
prefectly for a whole day before failing again.

Anyone have an idea of the type of thing that can cause this fault?

Rob

 

[Matteo]

The only thing consistent is that switching it off and back on will
almost always bring the red gun back, even if only for a minute or two.
It will also sometimes come back on by itself, and has been known to run
prefectly for a whole day before failing again.

Anyone have an idea of the type of thing that can cause this fault?

Rob

Not that im an expert, And you have probably already checked,
But is their a problem with the heating element for the gun possibly?

 

[Peter Jetson]

Now before asnyone states the obvious, I repaired monitors for about 12
months at one point and so I've tried all the usual things.

Do you have a cro? I'd have thought that it would be relatively easy to
find out where the drive for the red beam is present and where it is not
present.

Peter

 

[Rob Judd]

Do you have a cro? I'd have thought that it would be relatively easy to
find out where the drive for the red beam is present and where it is not
present.

Yes. However, when it fails the whole driver circuit for that gun shuts
down. So all I can tell with a CRO is that the signal isn't there any
more. I'm trying to get an idea of a typical component failure mode
thaty would cause such a fault.

Of course, I could just replace all the parts associated with the red
gun, and may end up doing that.

Rob