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Panasonic pt-47wx53 intermittent red color

Discussion in 'Electronic Repair' started by taylor1, Apr 8, 2013.

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  1. taylor1

    taylor1 Guest

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    I have a Panasonic pt47wx53 and have had it for some time. Lately I have been
    having an problem. The red color will go out and stay out for an hour or two.
    It will come back on much higher in intensity and sometimes go out again. I
    found that sometimes disconnecting the TV overnight, the red will come back,
    only later to go out again. It will last in some cases for 3 or 4 hours, and
    then go out again. I have ruled out the projector lamp in that the light
    comes back on. Can you give me some clue of what it is; am at the cross road
    of weighing the cost of repair (myself or a professional) vs. replacement.
    When no problems, the tv works very well, and the picture is great. I would
    really appreciate you in-put.


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  2. N_Cook

    N_Cook Guest

    Does it fade in and out or abrupt transition?
    Is the red still there but not saturated red?
    Have you tried replacing the lead/s & checking with different source
    signals?
     
  3. taylor1

    taylor1 Guest

    responding to
    http://www.electrondepot.com/repair/panasonic-pt-47wx53-intermittent-red-color-145957-.htm
    thanks for responding..when the color goes out it is abrupt. I have opened up
    the back to see that the lamp is completely out; no glow at the base. The
    only thing I have done is look for obvious signs of a short; no electrical
    tesing. What sometimes works is unplugging the set and allowing it to
    reset...sometimes it works, sometimes not. The red color will reappear after
    some time (anywhere from 5 minutes to 5 hours).
     
  4. John-Del

    John-Del Guest

    I have ruled out the projector lamp in that the light
    It's not a "lamp", it's a cathode ray picture tube, and you haven't eliminated that yet. Other than the fact they both generate light (and are under vacuum), lamps and CRTs have very little in common. It's not uncommon for CRTs to have intermittent issues, although Panasonic projection CRTs are uncommonly reliable. If this were a Sony, I'd suggest rolling it to the nearest landfill.

    The two most likely causes of a single color dropout are either a problem on the CRT socket board (bad connection or intermittent kine out transistor), or a bad G2\F block. The easiest thing to do at this point is to swap the G2 leads on the block from the red to either the green or blue, and see if a different color drops out. If so, replace the block.

    If not, you're going to need a service manual, scope and dmm and know how to use them. Careful, there's a lot of voltage on those CRTS..
     
  5. N_Cook

    N_Cook Guest

    I have ruled out the projector lamp in that the light
    It's not a "lamp", it's a cathode ray picture tube, and you haven't
    eliminated that yet. Other than the fact they both generate light (and are
    under vacuum), lamps and CRTs have very little in common. It's not uncommon
    for CRTs to have intermittent issues, although Panasonic projection CRTs are
    uncommonly reliable. If this were a Sony, I'd suggest rolling it to the
    nearest landfill.

    The two most likely causes of a single color dropout are either a problem on
    the CRT socket board (bad connection or intermittent kine out transistor),
    or a bad G2\F block. The easiest thing to do at this point is to swap the
    G2 leads on the block from the red to either the green or blue, and see if a
    different color drops out. If so, replace the block.

    If not, you're going to need a service manual, scope and dmm and know how to
    use them. Careful, there's a lot of voltage on those CRTS..

    +++++

    I read OP's lamp as discharge lamp then downloaded the SM from elektrotanya
    , saw 3 CRTs and stopped at that point.

    Loss of red on a colourwheel projector (thread farther back) I decided was
    wrong colour temp of the lamp , too blue although looks ok by eye, outside
    of the service adj range. Placed a rose pink filter over the output lens to
    trade a bit of luminance for a better red
     
  6. John-Del

    John-Del Guest

    On Tuesday, April 9, 2013 4:18:02 PM UTC-4, taylor1 wrote:


    I have opened up
    I missed that part when I responded. If the filament is out on the red CRTonly, it's a piece of cake. While it's possible to have an intermittent filament, the possibility of it happening on this series Panasonic is almoststatistically insignificant.

    Look at the bottom of the red CRT socket board, and check for bad solder onthe filament pins. The red filament might be wired to the green board, then down to the flyback area of the HV sweep module (most likely source of the filament in these models). Nick says the SM is available on line, so download that and trace out the wayward filament voltage.
     
  7. Guest

    Over the years I have come to not give advice to non professionals in the field, but these days it is getting hard to find anyone to actualy work on these CRT based sets, so here goes.

    The "coming back at increased intensity" is probably perceptual. Your eyes will adjust to the lack of red and then everything looks red. I could understand it happening if the set has AKB but I know of no Panasonic CRT based RPTVs that used AKB.

    I'll have to generally agree with what soemone said about Panasonic projection CRTs, they last. When there is a failure usually it is one tube and it is totally dead. It doesn't come back so that rules it out pretty much hereexcept for an intermittent short. That is very rare in Panasonic RPTVs.

    The first thing here is to beat the shit out of it. Take the front panel off and use a screwdriver or something to "disturb" the red CRT socket board.If it causes the red to come and go it's probably just a matter of resoldering the joints.

    However another thing my experience has taught me is that Panasonics have some pretty wierd failure modes sometimes. They are almong the only sets in which I have found transistors that simply stop transisting. I mean the ohmmeter will say they are good but they simply do not amplify. I do not know exactly why this happens more in certain brands, it could be where they buythe parts from or it may be their design. I had a no red Panasonic about ayear or so ago that was just that. A small signal transisor on the signal (not CRT) board that simply stopped working. There was no possible externalreason for its failure, like many times you see a bad transistor you find out that something else blew it. This was not possible in that particular circuit.

    Once solder joints on the CRT socket board are ruled out then you need to monitor voltages. Once the red cuts out, turn up the red G2 just to confirm it is not the CRT. Make sure there is NO red before you do this. It is highly unlikely but concievable you could have a shorted vertical yoke winding or an open horizontal winding. This is rare as all hell but in this case turning up the G2 would cause a phosphor burn. Be VERY observant, maybe even look directly in the tube to make sure. Turning up the G2 will give you red, but not with video. It will be what is called a slick screen with retrace.. Once you see that you know the CRT is not at fault so return the G2 control to it's original positon as closely as possible.

    After that, the simplest way for a non pro to proceed would be to get good with a soldering iron enough to change a transistor. One of the transistorson the CRT socket board will likely be on a heatsink. Maybe not, but it will at least be a "tabbed" transistor. That is most likely the video output.Exchange the red one with one of the ones on another CRT socket board. Then wait and see if the other color diappears or still the red.

    If still the red you're in trouble. If I remember correctly, Panasonics usually use emitter drive to their video outputs which means the transistor behind it has to handle some current. Without a print it can be hard but not impossible to find the set of three predrivers or whatever you want to callthem. On the PC board you might not be able to tell which is the red but you should be able to tell there are three of them and all the same configuration around. Rotate them.

    That means after you are sure that those are video drivers, take A, B and Cand switch them so it is not B, C and A. Know what I mean ? No matter which is which, when you rotate them the red one will either be in the green orblue circuit, the green one will be in either the red or blue, and so forth. Does the red still cut out or does another color ?

    If it is still the red I would highly suspect the jungle IC. A possible exception might be if the set has component inputs, but that's a longshot.

    This is long and involved sounding I know. That is why TV shops charge money. Actually at work I wwould use a scope and find it quick, but we do not even take in these sets anymore. We do service a couple a month on the road,but if it has to come in it doesn't, it goes to the tree lawn.

    Shame because the new stuff is so unreliable.
     
  8. Guest

    "A, B and C and switch them so it is not B, C and A"

    It should read "so that it is NOW......."
     
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