Mitsu 55511 Power Faults

[none]

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

 

[David Kuhajda]

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.

 

[none]

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

 

[Leonard Caillouet]

If the 24v line is low you likely have a bad convergence output IC or a bad
vertical output IC.

This series of sets is later than the ones that have lots of bad caps, and
we have not seen coolant problems in these.

Leonard

 

[none]

Are the convergence and vertical output ICs powered when the set is
first plugged in? I wouldn't expect that they are but I'll try looking
into this. Just in case this is not the issue I'll post more specific
details of the issue.

The set started exhibiting a problem where it would shut off as if it
lost AC power and then power back up to a standby state. It also did
this when in a standby mode, it would power off completely and then
come back on and the power LED would blink until it completed its
standby mode.

Eventually it started powering off and reseting rapidly so I unplugged
the set and came back to it later to see what was up. At that point when
I plug the set in the power LED just blinks continuously.

I do not have the schematics for this set and even though the set is
only a couple years old its not worth paying for service as the screen
has some burn issues. I've poked around checking voltages where they are
labeled and I've ran an ESR meter through the boards and replaced any
cap that was questionable but no luck.

I'm already looking at a few 1080p DLP sets to replace this box and not
one of them is a Mitsubishi. After owning a cheap RCA RPTV for 7 years
with no problems and only having this hi-def Mitsu for only a couple of
years and experiencing easily burned CRTs and now a power on issue I
will never buy a Mitsubishi set ever again.

If nobody has any further suggestions and I don't find the power on
problem I'll likely just drag the box out in the backyard and torch it.

burnin

 

[Leonard Caillouet]

Are the convergence and vertical output ICs powered when the set is first
plugged in? I wouldn't expect that they are but I'll try looking into
this. Just in case this is not the issue I'll post more specific details
of the issue.

No. The standby circuits are active, but the 24v supply is not until the
set is powered on.

The set started exhibiting a problem where it would shut off as if it lost
AC power and then power back up to a standby state. It also did this when
in a standby mode, it would power off completely and then come back on and
the power LED would blink until it completed its standby mode.

This sounds like a reset or standby supply problem. Likely a rather
inexpensive IC. Could be lots of other problems. Real troubleshooting is
needed.

Eventually it started powering off and reseting rapidly so I unplugged the
set and came back to it later to see what was up. At that point when I
plug the set in the power LED just blinks continuously.

I do not have the schematics for this set and even though the set is only
a couple years old its not worth paying for service as the screen has some
burn issues. I've poked around checking voltages where they are labeled
and I've ran an ESR meter through the boards and replaced any cap that was
questionable but no luck.

Screen burn is an issue with ANY brand CRT based product that is used
inappropriately. This is a fine set and these have had very few problems.
If you have burn-in, you had the contrast too high without varying the use
patterns for too long a period.

I'm already looking at a few 1080p DLP sets to replace this box and not
one of them is a Mitsubishi. After owning a cheap RCA RPTV for 7 years
with no problems and only having this hi-def Mitsu for only a couple of
years and experiencing easily burned CRTs and now a power on issue I will
never buy a Mitsubishi set ever again.

Mitsubishi has some of the best products available. If I were looking at
DLP sets I would certainly give them a look.

If nobody has any further suggestions and I don't find the power on
problem I'll likely just drag the box out in the backyard and torch it.

Troubleshoot or call a good mits tech. Torch it if it makes you feel
better.

Leonard

 

[none]

Thanks for the info Leonard, I'll go over it one more time to see if I
can find anything. I suspect it will be something inexpensive but I also
worry that if I call in a tech they'll just want to swap an entire board
at which point the set probably wouldn't be worth the expense to me.

As far as Mitsubishi's quality it isn't fair for me to judge it based on
a single set, but it is frustrating being on the wrong end of the
statistical curve. They do have a nice 1080p DLP set, and I may even
take a look, but as the saying goes once bitten twice shy.

Anyhow, thanks again.

burnin

 

[Leonard Caillouet]

email me at

first letter of my first name, followed by
first first 6 letters of my last name
at
d e v o y
n e t
dot
c o m


I said a "good" mits tech. Any that just routinely swap boards need to be
passed over. Now, sometimes, boards are not field repairable. That would
be the case with some of the digital boards. In those cases there is not
much you can do but swap boards. A good tech starts with the intent of
repair at the component level, usually. This is no different with Mits or
any other manufacturer's products, but you want someone who repairs a lot of
Mitsubishi to be sure that they will be efficient and effective.

If you have a catastrophic failure on a set this age, Mitsubishi might even
provide some relief, but you will have to have a good diagnosis before they
will even talk to you. I know of no company that has been as consumer
oriented as they have. They do go beyond the norm to kepp cusotmers.

Leonard