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Mitsubishi cs-2710ra vertical problem

Discussion in 'Electronic Repair' started by ladybug, Aug 20, 2006.

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  1. ladybug

    ladybug Guest

    My trusted Mitsubishi cs-2710ra died, it displays thin horizontal bar
    on the middle of the screen. I can see picture elements in the bar .
    I'm debating if it makes sense to fix it or just trash it. I'll attemt
    to fix it first by myself but I need help to troubleshoot it. Please
    help me to troubleshoot it or give me suggestions what to look for.

  2. longman

    longman Guest

    Check the electrolytic capacitors on the board that the yoke coil plugs
    into. Most of the time that is the problem. You may need to replace
    more than one.
  3. ladybug

    ladybug Guest

    Do I need to unsolder caps for checking? How can I see if cap is bad
    with multimeter? If you can get a hold of schematics can you tell me
    which caps to check?
  4. rb

    rb Guest

    It's best to use a ESR meter for finding bad caps
  5. Actually an ESR meter will not identify all or even most of the bad caps in
    this set. Some will have high esr, most will be physically leaking
    electrolyte, and some will be low in capacitance. This problem may be
    caused by leaky caps at the vertical output IC and/or in the 12V supply.
    Ther will be at least a dozen more that need to be replaced or more problems
    will be occurring soon. The circuit traces that are corroded from the
    electrolyte leakage will need to be repaired and all of the residue from the
    caps will need to be washed from the board. We fix these all the time and
    they are a "pay me now or pay me more later deal." We don't even touch tem
    if the client does not want to pay to have all the bad or failing caps
    changed. Just fixing the vertical circuit is a sure way to get a recall in
    a few weeks or months with an unhappy client.

  6. ladybug

    ladybug Guest

    Does anyone can point me to a repair manual or schematic?
  7. You can get it from Mitsubishi, but it will likely be a waste of $$$. It
    will not tell you how to fix the set.

  8. kip

    kip Guest

    Why dont you read what people have posted for you.

  9. ladybug

    ladybug Guest

    I did read. I just don't want to replace every single cap "on the board
    that the yoke coil plugs
    into". I want to be more specific because I need to get new caps
  10. No need to replace every single cap. I said that you will find perhaps a
    dozen bad caps in the set. Two dozen if you are very unlucky. I also said
    that you can fix the immediate problem with just a couple of caps in the
    vertical ouput stage and perhaps one on the 12v regulator.

    No tech who fixes these type of problems would need the service manual
    unless a trace was corroded away beyond recognition of where it went. In
    order to fix this set you need to:

    1. Identify the leaky, high esr, and low value caps, which will require an
    ESR meter, a capacitance meter, and reviewing the instructions posted
    several time in the past for finding leaky caps. Google the group for
    Mitsubishi, capacitors, and my name for instructions on finding the leaky

    2. Clean the board of electrolyte and corrosive residue.

    3. Repair the damaged traces and bad solder joints.

    4. Replace the bad caps and perhaps the vertical output IC.

    If you don't check all of the caps for leakage you will be fixing it again
    in a few months.

    Now you have been given much more information than you will find in the
    service manual regarding solving your problem. You can spend the $$ if you

  11. ladybug

    ladybug Guest

    I replaced 5 leaky caps that I found but it didn't change anything. I
    suspect that vertical output IC went kaput. After all it died suddenly
    without gradual picture srinking. Is it LA7838 chip? Is there a way to
    test it with multimeter? What is a good place to get a replacement?
  12. If you want serious help, post some specifics. You probably did not get all
    of the caps that are bad. There will be at least a dozen. Do you have both
    the 12v and 28v supplies at the output IC? Which caps did you change?

  13. ladybug

    ladybug Guest

    I replaced C458, C450, C460 all 100uf. Also C559 and 2G1. I defenately
    missed some.... On the IC I have 12v on pin one but no 28v. Is it
    supposed to be on pin 8? Nothing there.
  14. Tech Data

    Tech Data Guest

    Then you need to backtrack to the flyback. You have an open current
    limiter, probably a 1.2 ohm 1/2 watt. And yes, if it's an LA7838 pin 8
    is your primary VCC and should be 28 volts or so.
  15. ladybug

    ladybug Guest

    Also trace from c458 to pin 9 was corroded and read open. I got that
    taken care off.
  16. ladybug

    ladybug Guest

    You're right R558 reads open. Why did it burn and where can I get a
  17. Now look over to the left of the board as you see it from behind and find
    the leaky caps around the heat sink near the front of the board. There will
    be several, perhaps about 10. There are two that will be on the vertical
    board with the regulator. If you don't get them , and the rest of the leaky
    caps on the main board, you will be doing this again soon. Check ALL of the
    black colored polar electrolytics made by rubycon, nichicon, or sme.

  18. ladybug

    ladybug Guest

    There are plenty of leaking caps on the front left of the board where
    you said but I don't see any vertical board with the regulator. Where
    is it? I'm also out of replacement caps and need to buy a bunch for
    this repair. Can you recommend a place to buy and preferable type/brand
    of electrolytic caps? I also need a 1.2 ohm current limiter
  19. I may be thinking of another set. I buy most of my caps from Tritronics
    which is good if you are on the east coast. There are lots of similar
    distributors all over. Get 105 degree caps. They don't stock 35V caps,
    just use 50V instead. None of these will matter.

  20. ladybug

    ladybug Guest

    Looks like almost all the caps that I have made by rubycon. I'll try to
    replace most of them. How can I get off the board leaked acid? Do I
    need to replace caps on the tube board? None of tube caps seems to be
    leaking. What is the correct part for 1.2 ohm current limiter?
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