jakdedert said:
Many, many LCDs suffer from problems related to electrolytic capacitors
failing in the switchmode power supplies. I've revived a couple by
changing out (and uprating) those caps. Often, the fault is obvious
when you examine the power supply board. The caps will be swollen or
leaking...sometimes even burned by proximity to heat-producing
semiconductors.
That's a design fault that I've noticed in at least one of the units
I've serviced. Upgrading the caps produced a fix, but I wonder if I'm
going to have to do it again. If so, I'll attempt to improve the air
flow through the unit to prevent further problems.
Your symptoms are consistent with the above. Sometimes the caps fail
without visual indication. If you have no way of testing them,
'shotgun' replacement is perhaps the easiest strategy. Go for the big
ones, especially those with high voltage ratings (over 50 volts).
Replace with high-quality caps, temperature rated at 105C.
jak
Well, it was a LCM-19v7. It would turn on for 1 second or so then shut
down. Disassembled it. It took a awhile to figure out how. Four screws
on the back outside frame. one screw under the base mount. could not get
to that one and took me awhile to figure out how the base mount comes
off. There are two trim pieces that snap on on both sides of the base
mount that are compression fit and snap off. after they are off, it
exposes 3 screws on each bracket that will remove the bracket. After
that, the case is a clam shell with compression fit retainers all the
way around which have to be gently pried on to remove the shell.
The inside then has two metal sheilds over the two control boards which
have to be removed. you have to take the screws off the HD-15 and the
HDMI connector and power to get the main shield off along with some
small screws on the perimeter. The secondary shield will only come off
if you undo the latches at the bottom of the main LCD assembly to pry it
up slightly.
After all this work, the boards are pretty straight forward. A PS board
and a control board. The PS board had 3 220ufd@25v caps with the top
bulged off. It also had two 1000ufd @25volt caps that were bulged or
were blown out at the bottom. A trip to the recycled parts bin
(you do save those higher value caps out of the junked stuff don't you?)
put the unit back in operation. All the bad caps did not register on
the ESR at all. What junk!
At least i got picture now.
bob
