I just wanted to pass on my experience with a Magnavox projection TV I
recently fixed. Now, I do want to stress that unless you have an
understanding of electronics and know how dangerous working around
high voltage is, then please don't try to repair a TV yourself. You
may cause more harm to the circuits, and possibly yourself.
My father-in-law had me look at this TV, it was his main set, about 10
years old. I'm not a TV repairman, but I do have a 2 year electronics
degree and I am employed in the semiconductor industry repairing
lithography equipment. So automatically I'm the one in the family that
gets called went the TV/radio/computer stops working.
I took a quick look at it, will not power on, was working fine the
night before. My father-in-law mentioned that the night before, a text
message came on the screen "BATTERY LOW". Wow, he thought, that is one
smart TV to know when the batteries in the remote are low! So I do the
normal checks, fuse was good, power to the outlet was good, no
thunderstorms to knock out the circuits.
He mentioned that he did call a repair service and they quoted $250
plus time to replace the main board, they didn't even look at it, just
a shotgun approach. I inquired about purchasing the board directly
from the manufacturer, $600, because they will not take the old board
back from individuals, only certified repair shops.

So when I started looking at power supplies, etc., that Battery Low
message kept me wondering. I did find a quarter sized watch battery
SOLDERED to the main board, UNDER metal shields, on BOTH sides of the
circiut board.

After carefully removing the shields to access the battery, I
unsoldered it and placed a 3V, AA battery pack from Radio Shack in its
place. Would you believe the TV powered on! This set would have been
thrown out for a $3 battery. Now this unit is over 10 years old, and I
am surprized that the battery lasted this long. And here is the
kicker, eventhough the battery was low and I removed it from the
circuit, it still retained the channel programming memory. Then what
the hell is it's purpose! I do have the full schematics from Magnavox
(Philips), it doesn't even go to the memory chip (EPROM), it does go
to a clock/ram chip.

So the moral of the story is, heed all messages the TV gives you. If
you have a TV that will not power on and the fuses are good, ask the
repairman about the battery on the board.

Does anyone else know of this 'problem' on other sets? I can't believe
that this would be designed into the circuit like this. A battery has
a known life, in use and a shelf life. This should have been
accessable and in a holder, not soldered. But I guess it's better
profits when a new set is purchased as compared to a new battery.

Regards..
Mike...