I'm wanting to determin if my power supply voltages are correct on my
dead LCD TV. On my power supply board the output voltages are printed,
but since the set doesn't turn on, the only voltage I see present is 5
volts on the stand power supply pin.
I realize the power supply isn't completely turned on until the
microprocessor on my video board sends it the correct turn on pulse,
but isn't there more I can do aside from assuming the video board is
likely defective. I checked ESR on all capacitors, looked for shorted
diodes and transistors, burnt resistors, etc. What is a high failure
item on the video board which might cause this? The set doesn't come
on for even a second.
This is a Westinghouse model SK32H240S

Thanks in advance.

"Dave" wrote in message
...
I'm wanting to determin if my power supply voltages are correct on my
dead LCD TV. On my power supply board the output voltages are printed,
but since the set doesn't turn on, the only voltage I see present is 5
volts on the stand power supply pin.
I realize the power supply isn't completely turned on until the
microprocessor on my video board sends it the correct turn on pulse,
but isn't there more I can do aside from assuming the video board is
likely defective. I checked ESR on all capacitors, looked for shorted
diodes and transistors, burnt resistors, etc. What is a high failure
item on the video board which might cause this? The set doesn't come
on for even a second.
This is a Westinghouse model SK32H240S

Thanks in advance.

On many, although not all, LCD TV sets that I've had the 'pleasure' to work
on (!) the standby supply produces +5v and +3v3. Normally, when you have one
that won't come out of standby (do you actually even get a standby light
showing?) the first thing to do is to locate the standby switching line to
see if that is toggling. If it is, you then need to look at each individual
output rail from the power supply to see if they start to try to come up.
Often, they will, but fall over again so quickly that you don't see any
activity at all in terms of the set coming to life. The rails are normally
something like +3v3 switched, +5v switched, +12v, +24v high current (for the
backlight inverter) and +33v.

If the power supply is trying to start, then the next thing to do is to
unplug the backlight inverter board. It is common for these to fail, and if
they impose a heavy load on the 24v rail, the power supply will shut back
down before it ever really gets going. Another common failure for a heavily
loaded rail, is a failed audio IC.

In general, LCD TV power supplies are *very* heavily self protecting, and
they will either shut back down very quickly, or not even come up at all (as
far as you can see) if they detect the slightest thing wrong with any of
their rails - thats over-voltage, under-voltage, or excess load.

It can be very tricky to get to the bottom of what's causing an apparently
dead LCD TV. I have also had system control micros fail, and also corrupted
EEPROMs causing startup problems.

Arfa