Art wrote:



"Baron" wrote in message
...
Hi Guys,

I have a problem with the backlights on a 17" LCD monitor going out
after about 30 seconds. Turning off and back on causes them to come
back on but only for 10 seconds or so.

I took the thing apart and one of the two backlight PSU is getting
very hot very quickly. Any ideas anyone ?

Thanks in advance.
--
Best Regards:
Baron.

Either the lamps are failing and causing the ballast to overheat, or
the ballast itself is failing. Suggest swapping the ballast to the
other lamp and see if you maintain the same heat rise, if so then you
know the lamps
probably are ok. Overheating ballast could be caused by failing
electrolytic capacitors or other devices.

I thought electrolytics, but there is only one on this board and its
common to both PSU. I'll try swapping the lamps around and re-check.

Would a failing lamp be any dimmer ? The light across the screen seems
equal. No dark areas or bands. Turning down the brightness doesn't
alter the length of time they stay on. Another thing I noticed was
that the output capacitors, there is two in series for each lamp, seem
to be very small values. They are marked 18J 3Kv. I assume that is
18pf 5% 3000 volts working.

--
Best Regards:
Baron.