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Mitsubishi TV

Discussion in 'Electronic Repair' started by Don Raggio, Jan 2, 2004.

  1. Don Raggio

    Don Raggio Guest

    I have a ten year old Mitsubishi 45" Tabletop Rear Projection TV Model
    #MVS4571. When I turn on the TV the picture rolls and it out of focus for
    about 15 minutes until it "warms up". After that the picture is O.K. but
    sometimes goes out of focus. Is there anything I can do to adjust the
    picture? In the old days we had horizontal hold and vertical hold. Thanks.

    Don R.
     
  2. David

    David Guest

    Step #1, ESR every single electrolytic capacitor in the tv set.
    Step #2 replace all the capacitors on the PIP circuit board.
    Step #3 troubleshoot any remaining failures.
     
  3. Well, almost correct, David, but ESR tests will not get many of the
    capacitors that are physically leaking electrolyte, which is the bigger
    problem in many of these sets. You have to visually inspect them and/or
    heat the leads and smell the results. I have seen many caps that are
    leaking electrolyte that pass all tests, including ESR.

    Leonard Caillouet
     
  4. Asimov

    Asimov Guest

    "Leonard Caillouet" bravely wrote to "All" (02 Jan 04 20:38:30)
    --- on the heady topic of "Re: Mitsubishi TV"

    The problem with most esr meters is that they use a rather high
    frequency of about 100K Hz to keep the reactance of small electro values
    negligible. The problem with this strategy, in my experience, is that
    large value electros can test good with the higher frequency because the
    outside layers can behave as a perfect small electro and yet indicate
    very little esr, since the inner layers are in effect bypassed. Not all
    bad large electros behave this way but enough do to make a difference.

    As such having a range of about 3 test frequencies would be helpful.
    For example 100K Hz is great for electros of 10uF and less to about
    0.1uF. 33K Hz is good from about 10uF to about 470uF and 10K Hz for
    anything larger than about 470uF up to about 10mF. Then 3.3K Hz for even
    larger values, etc.


    LC> From: "Leonard Caillouet" <>

    LC> Well, almost correct, David, but ESR tests will not get many of the
    LC> capacitors that are physically leaking electrolyte, which is the
    LC> bigger problem in many of these sets. You have to visually inspect
    LC> them and/or heat the leads and smell the results. I have seen many
    LC> caps that are leaking electrolyte that pass all tests, including ESR.

    LC> Leonard Caillouet


    .... Resistance Is Futile! (If < 1 ohm)
     
  5. So do you know of any available testers that have these options? Why don't
    you suggest that Bob Parker update his design...

    Not that it matters much in this case. The point was that in many of these
    sets the problem is due to the electrolyte itself and not the performance of
    the cap. I tested one just a few days ago that had one leg mostly corroded
    off and it passed all the tests on my Sencore. You can test any way you
    want and if you don't LOOK for the obvious problem you won't be successful
    in fixing these sets.

    Leonard Caillouet

    "Leonard Caillouet" bravely wrote to "All" (02 Jan 04 20:38:30)
    --- on the heady topic of "Re: Mitsubishi TV"

    The problem with most esr meters is that they use a rather high
    frequency of about 100K Hz to keep the reactance of small electro values
    negligible. The problem with this strategy, in my experience, is that
    large value electros can test good with the higher frequency because the
    outside layers can behave as a perfect small electro and yet indicate
    very little esr, since the inner layers are in effect bypassed. Not all
    bad large electros behave this way but enough do to make a difference.

    As such having a range of about 3 test frequencies would be helpful.
    For example 100K Hz is great for electros of 10uF and less to about
    0.1uF. 33K Hz is good from about 10uF to about 470uF and 10K Hz for
    anything larger than about 470uF up to about 10mF. Then 3.3K Hz for even
    larger values, etc.


    LC> From: "Leonard Caillouet" <>

    LC> Well, almost correct, David, but ESR tests will not get many of the
    LC> capacitors that are physically leaking electrolyte, which is the
    LC> bigger problem in many of these sets. You have to visually inspect
    LC> them and/or heat the leads and smell the results. I have seen many
    LC> caps that are leaking electrolyte that pass all tests, including ESR.

    LC> Leonard Caillouet


    .... Resistance Is Futile! (If < 1 ohm)
     
  6. You have to visually inspect them and/or
    Another thing that can be done is to look at the circuit traces underneath the
    mainboard. The leaky electrolyte can seep past the solder joint and can
    corrode the coating and the traces, which makes a normally green trace look
    dark brown or black. After removing the cap, any and all leaked electrolyte
    must be cleaned off as best as possible, including scraping off the electrolyte
    stuck on the underside of the board, but being careful not to sever any of the
    traces in the process. It will remove the coating that insulates the traces,
    though. - Reinhart

    P.S. This reminds me of an amusing anecdote involving my Sony SVO-160 with
    those Elna LongLife and Duorex II caps. One day, my sister was complaining why
    my room was having this strong fishy smell. I went in the room and all I could
    say was, "aww, man!" I knew that something in my room that had power had a big
    failure involving caps, which turned out to be my VCR. I had to replace every
    single LongLife and Duorex capacitor in the VCR as they all had leaked! After
    that, no problems.

    Crappy Elna caps!
     
  7. BWL

    BWL Guest

    Also don't forget to check the circuit boards and CRT assemblies for coolant .
    This chassis is notorious(?) for leaks...
     
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