David Kuhajda wrote:
"none" ""burnin\"@(none)" wrote in message
...

Hi,

Are there any Mitsubishi RPTV gurus in the house?

I have a Mitsubishi WS-55511 rear projection TV that started to shut
itself off intermittantly. It would do this even when the unit was off in
standby. What ever was going out finall died and now the power LED just
continually blinks when it is plugged in, no more intermittant power
failures but now it wont power up either. Pressing reset on the front of
the system the LED goes off and then comes on and start blinking
continuously again.

Without schematics and a manual I can only get so far and its not far
enough. There are service manuals available from some russian and chinese
web sites but I just don't think I'll take my chances with them.

So before I call in a tech who has the manuals I thought I'd check around
to see if anyone around here has manuals or an idea of what to look at.

I've checked several points which are labeled on the boards and so far the
only discrepancies I can find are a 24V connection on the signal board
which has no power, which may be normal, and the powergood signal from the
CPU to the signal board is 0V. I check voltages inside the CPU cage and
they all looked good, 3.3V, 5V, and 12V.

burnin


Given that it is a Mitz RPTV, a going over with a good ESR meter and
checking any capacitors. It is also prudent to check the main power supply
circuit for proper function. I would not be suprised if there is liquid
coolant on the boards somewhere.


I picked up an DCR/ESR meter and starting going over the boards. I've
gone through most of the caps on the two power supply boards and
replaced a couple that were marginal but still nothing. I'll continue on
with the signal board and the small PCBs attached to the power supply
PCBs.

As far as coolant leak, at first I didn't see anything but as I was
going over the boards with the ESR meter it appeared there was a greasy
looking film on the center board (looks the low voltage DC supply with
the audio amplifier). So does a good degreasing usually solve the power
up problem is it is leaked coolant?

I've also done more DC voltage checks and on the signal board there is a
connector labeled FL which has a +24V and Flash connection which go to
the low voltage DC board and the high voltage boards. The +24V is
reading 0V and the Flash is reading 1.35V. Does anyone know if these are
normal readings when in a powerup state?

Thanks,
burnin