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Mitsu 55511 Power Faults

Discussion in 'Electronic Repair' started by none, Jan 7, 2006.

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  1. none

    none Guest

    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
     
  2. 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.
     
  3. none

    none Guest

    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
     
  4. 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
     
  5. none

    none Guest

    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
     
  6. No. The standby circuits are active, but the 24v supply is not until the
    set is powered on.
    This sounds like a reset or standby supply problem. Likely a rather
    inexpensive IC. Could be lots of other problems. Real troubleshooting is
    needed.
    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.
    Mitsubishi has some of the best products available. If I were looking at
    DLP sets I would certainly give them a look.
    Troubleshoot or call a good mits tech. Torch it if it makes you feel
    better.

    Leonard
     
  7. none

    none Guest

    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
     
  8. 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
     
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