I should have tested more thoroughly before posting. Turns out the power
supply is good - all three output voltages are normal. The problem must be
in the mainboard - the power light comes on but nothing happens. So it looks
like a dead end for this set.
What I might try to do is fit the power supply from this set into another
one, rather than building an external supply....

"Arfa Daily" wrote in message
...

snip


From a personal perspective, I 'grew up' with analog power supplies
(often using vacuum tube rectifiers). These were inefficient, but
easy to repair. The switch to SMPS supplies required more
sophisticated techniques, but in the end was not that much more
difficult, even for the multiple output supplies found in PCs.

At this point I am finding the supplies in LCD TVs to be extremely
difficult to troubleshoot safely and effectively.

PlainBill

Agreed. The key to it seems to be obtaining schematics. I offer a trade
repair service on a particular LCD power supply board, but I am only able
to do that as a result of hours of painstaking research to find schematics
to cover all the variants. I then spent a long time analysing just what
made this supply tick (figuratively, not literally !! ) and then sat down
and designed a test jig and a set of adaptor harnesses to allow the
different variants to all be repaired using that jig. I can pretty much
crack most problems on them in fairly short order now, but still get the
occasional one that gets the better of me. Just yesterday, actually ... I
have one at the moment that has a really odd fault. The PFC supply won't
start up at full supply volts. Turn it down on a variac just 10 volts, and
it will start every time. If you then turn back up, it keeps running, but
the PFC supply starts to squegg, and the 390v rail drops to around 340v.
At the same time, the 24v secondary side rail drops to around 23v, but
curiously, all the other rails stay spot on. That might be the clue to
what's going wrong, as the 24v rail is normally *very* tightly regulated.
I would add that the problem occurs whether there is a load on any of the
rails or not. It'll be an interesting one to eventually find when I have
the time, but in the meantime to get my customer out of trouble with his,
I've had to do him a swapout.

Arfa