PlainBill wrote in
:

On Sat, 25 Apr 2009 23:26:22 -0700, John E.
wrote:

What fails most commonly in inverter circuits in, for example, 18 inch
LCD displays?

http://www.lcdrepair.us/1800inverterKUBNKM045A.html

I know anything *can* fail. But is there a common, high-frequency
failure component in these inverters?

Thanks.
One common failure in some designs is a chain reaction failure. Poor
quality caps are used in the power supply and the inverter. As the
ESR rises the drive transistors in the inverter tend to overheat,
eventually shorting and blowing the input fuse on the inverter.

the TEK 1720,1730 NTSC TV waveform monitors had this problem,except all the
other supplies would rise,the HV xstr would overheat,burn the PCB until it
became conductive,and then put the switcher into 'click' mode.I used to
Dremel out the carbonized part,fill with epoxy,and put down new runs and
eyelets,and changed the +5V filter cap to a better grade and a larger
capacitance value.Never had any repeats after that.


Replaceing the low quality caps, the transistors, and the fuse results
in a working monitor.

The Westinghouse Westinghouse L1975NW (and equivalent Acer model) -
identical monitor except for the plastic - have this problem.

PlainBill




--
Jim Yanik
jyanik
at
kua.net