No, there's nothing at the enable line at power up. Since a primary
winding was bad I believe the driver IC for that section is damaged
causing the feedback to disable the backlight. No transformers were
damaged when removed, I checked them all with my Sencore LC77...thats
how I found the bad one. I can verify this by scoping the primary side
drive when forced on.
All other voltages are there. 24v,12v, 5v, and 5v stby.
I don't have an encyclopedic knowledge of all LCD TVs, but in my
experience there usually was no feedback from the inverter to the main
video board. The usual sequence goes something like this:
When the TV is plugged in the standby power supply (5v stby) comes up,
which starts the standby controller (often a part of the main control
IC). This may then briefly turn on the main power supply, check for
problems, then turn off the main power supply. The standby controller
then monitors the remote sensor and control buttons for an 'ON'
command. When one is received the main power supply is turned on, a
self test is run and if everything is OK the inverter enable line is
driven high. If the self test fails typically an LED is flashed to
indicate an error.
Typically the inverter is supplied by the manufacturer of the LCD
panel, and several versions may be found on a given model. A quick
search on eBay shows at least three different models of inverters,
including one that was notorious for blowing drivers, and another that
was notorious for failures of the transformers.
An additional point - some models of Sanyo are known to have a 'lock
up' mode. If a failure is detected, they will shut dwon and refuse to
restart until a particular reset sequence is entered via the remote.
One point you did not mention - does the power button on either the
remote or the control panel switch the main power supply off and on?
If it does, one technique I use is to hook a signal source (video
game, DVD player) up to an input, turn the TV on, then use the input
button to cycle through the inputs to see if sound is heard.
PlainBill