My 4-year old 19" Dell (Sony) monitor is having some HV problems. Yesterday
my 12-year old daughter said it "popped" a couple times and the screen
flashed/changed size along with the pop and then returned to normal. She
came to get me immediately and when I got there it seemed to be fine for
about 5 minutes, then popped once and lost the image completely. I turned
off the monitor right away at the switch, waited a few minutes, then tried
to power it back up. It turned on, lost the picture within a fraction of a
second, and began emitting a new barely audible sound. This sounded to me
like a high voltage discharge so I disconnected the unit from the computer
and carried it down to my bench for further analysis.

I opened up the monitor case, removed the right (looking from the rear)
metal HV shield and then plugged in and turned on the monitor without a
video input signal under a low light situation to see if I could identify a
flash/spark that was accompanying the sound. This proved to be very easy
since it was a glass discharge protector located at designation SG901. (It
lit up pretty much like a neon bulb...) I kept it powered up just long
enough to verify that none of the other protectors on the CRT socket board
were lit and that the sound was coming from only the one device. I saw no
obvious arcing or shorts anywhere. My assumption here is that the HV output
has drifted high and the discharge is the protection which was designed to
kick in working as expected.

I have removed the main board, but do not have a schematic. I'd like to
start with the assumption that the protector is working as designed and
check the values of the critical components in this circuit against their
specified values. Unfortunately, I do not have a schematic to identify
which ones they would be. I'm hoping that someone can send me the schematic
and/or their recommendation on fixing the problem.

Prior to encountering this issue, the monitor had worked flawlessly and I
would prefer not to have to purchase a replacement. Thanks in advance for
your assistance and thoughts.

Bob