Robin Taylor wrote:
actually there is that diode just after the smps transformer but i don't know
exactly if it is operational or not as it didn't grab my attention. i'll
check on it in the morning.

The Diodes after the the SMPSU are secondary rectifiers, they're most
probably ok.

You are looking for a big diode like this:
http://www.nxp.com/acrobat_download/...ts/BY448_2.pdf
near the line output transistor, this is the transistor most likely
screwed to the aluminium box/heatsink surounding the line output
transformer. http://en.wikipedia.org/wiki/Flyback_transformer

I have seen this diode fail, in a few monitors, when it fails it
effects width and east/west correct,(pincusion).
All this said its been at least 10 years since I was fixing monitors.

Good luck,

Robin

i red this paper which gave me an idea about the larger picture of horizontal
sync. http://www.repairfaq.org/sam/reppic/horiz-tv.pdf, and i think it said
the same as you suggested, there is a problem with a peripheral component
around the flyback transformer. i also checked on the flyback trans. and the
components around it, i found the damper diode and it checked right it's
operational, but it looks like a regular diode except for it's a little bulky
and brownish in color. i found also another diode that looks like the one the
datasheet you posted mentioned, it has a glass casing and it's oval in shape
but it's very small and white and it's operational too.

the numbers of both the diodes are;

1. rg4a bulky one 2. 33ipn small one

finding that every thing is fine with these, i tried to check every component
around the flyback transformer. every thing checked ok, nothing seemed
damaged, there were two more diodes and they were ok, there was a coil and it
checked ok too. and a n-p-n BJT and it checked ok too. an elecrolytic
capacitor was there too and it was fine, but i'll recheck on it again may be
replace it, i already got a new spare one.

not only this i checked on all the FETs on the pcb and they all were n-
channel type and they were fine. i have diode checker in my multi-meter and
it shows the biasing voltage if the diode is operational. all of the solid
state devices i've checked were ok. all the BJTs around were ok too, and the
diodes that were away from the flyback transformer were ok too. everything
just looks fine, no burnes, no exploding or leaking devices, or damaged not
even a small resistor, which adds much to my confusion. does this have any
thing to do with damage to the flyback trans. itself?

hope any solution that fixes this situation appears in the horizon.

thanx

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