Question about Toshiba Televison & Video

7 Answers

I have a 2 year old Toshiba FSTPURE 27" flat tube CRT tv. The problem is that there is no vertical scan---the picture is a single horizontal line in the center of the screen and all other systems appear to be working. Two questions. What is the likely problem and is it repairable at a reasonable price? I am an electrical engineer and spent 45 years in the computer hardware business so I am willing to tackle tv repair on my own.

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  • 3 more comments 
  • msternx Jun 30, 2008

    THIS PROBLEM DOES NOT REFER TO A PROJECTION TV.





    IT IS FOR A STANDARD BROADCAST 27"CRT TV.

  • msternx Jun 30, 2008

    Thanks for the quick response but the answer is too vague. Without a schematic it is impossible to know which is the vertical IC
    or which resistor you are referring to.
    What else beside the vertical control circuit
    could be the problem? Could it be the high voltage supply---although probably not since the horizontal scan is working.
    I need enough info to fix it.

  • msternx Jun 30, 2008

    One additional piece of info----When the picture becomes a horizontal line, I can get the picture back by turning off the TV and
    turning back on after several minutes. It will then operate for 5 to 10 minutes before failing. I assume that this implies a fault that is marginal and heat sensitive.

  • msternx Jun 30, 2008

    The model # of the TV is 27DF46. I haven't looked for the chassis # but the S/N is
    BAB614022413 A and was manufactured in Feb 2006.
    Maybe the S/N reveals some info about the chassis #.

  • msternx Jun 30, 2008

    Hi Robotek,

    It looks like the Premtech solution is detailed
    enough to attempt a fix. I have only a couple of simple questions. When the back cover is removed, is the main board containing the LA7847 easily identified and is it easily removable--is the board connected to the rest of the TV thru a set of connectors?
    (I am aware of the high voltage even when powered off).
    It is late here so I will be back to you tomorrow. We are getting close. Thanks

×

7 Answers

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You have to look for dry solders in the region between vertical output transistor and primary side of the flyback (LOPT) transformer. Youd dont need a service manual for this. Just re-soldering circuits as Benimur suggested will do the trick..

Posted on Jun 30, 2008

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  • Master
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Hi there

Try replacing the electrolytic capacitors in the power supply section. I started with replacing (2) 860uf 180v caps just after the bridge rectifier and continued along the circuit. Some (15) or so capacitors later,it finally cleared the the horizontal bars and lines and the high pitched noise. It also fixed another intermediate problem of no video, when turning on the power.

Thank you for using FixYa. Have a nice day and please remember to rate this solution as FixYa if it helps you.

Thanks
Dustin Ellse (BearWeb)

Posted on Jun 30, 2008

  • Dustin Ellse
    Dustin Ellse Jun 30, 2008

    Here is a picture of what they look like:


    Thank you for using FixYa. Have a nice day and please remember to rate this solution as FixYa if it helps you.

    Thanks
    Dustin Ellse (BearWeb)




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  • Expert
  • 243 Answers

Ok on the dboard This is your most probable cause after looking at the circuit diagram you need to replace 4 10V10 CAPACITORS.
the 2 ZENER DIODES # 10.0V 1W .
and this IC SEMICONDUCTOR LA1460 kit and you should be set.


test em to make sure and replace them as needed that website has anything that can be blown.


Hope this helps,

Nate

Posted on Jun 30, 2008

  • 1 more comment 
  • Nathan Ayers
    Nathan Ayers Jun 30, 2008

    But this is your most likely problem that i laid out to you. Im not just giving you what it could be. Im giving you what it is, As i trust with your experience you described. This should be no problem for you.

  • Nathan Ayers
    Nathan Ayers Jun 30, 2008

    i have access to the circuit diagram if you need help on a replacement walk through.

  • Nathan Ayers
    Nathan Ayers Jun 30, 2008

    That IC isnt even in the unit Robotek i Have the circuit diagram do you? or you just blowing smoke. Cause none of what your saying is right yet your trying to discredit someone. You dont know much about IC replacement if all you have to do is replace an ic theres a little bit more to the kit then that. You need a diode and a cap or the IC will blow again. But you do your thing if it helps.

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  • Master
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Hi

The verticleICis mounted on a heatsink, and you will find thicker wires connected to the yoke plugged in nearby. Cahnge all the capacitors about the area also, as they have a tendency to blow chips,or cause other problems. This about does a vertical stage repair. Take the back off and have a look for the yoke connection like I have said.Check before anything else that the chip itself is not just dry jointed. This will cause vertical collapse also. The only other thing may be an open circuit yoke.

I am more than happy to answer any other questions you may have about it, please get back to me here, or use the ASK function to go straight to me :) If you are still unsure, have problems, or we need to look at the situation more deeply, then before you give a rating for this advice, hit the ASK button Thanks for using FixYa, If you consider the advice I have given you as sound, a FixYa rating is a great reward for my efforts to help you. Cheers.

regards robotek

Posted on Jun 30, 2008

  • 8 more comments 
  • Graeme Ross
    Graeme Ross Jun 30, 2008

    It is a fault in the vertical not horizontal stage, so focus your efforts there to begin with.

  • Graeme Ross
    Graeme Ross Jun 30, 2008

    yes, the fault may be marginal. Capacitors are a likely cause of this condition also. I generally just rebuild the area, clean old heatsink paste away, and use new compound. I use 2% silver content solder for its better heat stress strength

  • Graeme Ross
    Graeme Ross Jun 30, 2008

    DON'T FORGET - DANGEROUS VOLTAGES ARE PRESENT
    even with power disconnected !!! Be sure to Work electrically safe.


  • Graeme Ross
    Graeme Ross Jun 30, 2008

    If the problem comes and goes however, it is probably more likely to be dry joints. Start with resoldering first, then if it does not improve capacitors and vertical IC would be my call

  • Graeme Ross
    Graeme Ross Jun 30, 2008

    Here is another repair method relaying the same message about the verticle IC by one of our Top Experts, Premtech

    it's most likely the the vertical IC an
    LA7847-E has probably become ring-cracked at the point where the pins
    are soldered to the pc board.

    Depending on how long it has been
    allowed to arc the IC may have failed also, but they are not terribly
    expensive or difficult to repair - at least not here in the shop.

    The
    main board has to be removed. Locate the vertical IC - it will be
    mounted to a metal heat sink and the IC will be stamped LA7847. Then
    turn the board over and inspect where the pins are soldered to the foil
    side of the board. One or more will look ring cracked or fractured all
    the way around the pin. At this point you have two options, carefully
    reflow solder over each pin and put it back together or replace the IC
    by de-soldering it and removing it from it's heatsink. remember to use
    a good heat sink grease when applying the new IC.. There should also be
    a couple of caps in pretty close proximity to that IC... One should be
    about 50v/100uf and in the shop here we test em all... You might also
    just replace that one for good measure - they're not expensive either...


  • Graeme Ross
    Graeme Ross Jun 30, 2008

    it can be said that there are many ways to skin a cat, there is only one way to skin this one. The solutions given relating to the verticle output IC are correct. I hope that the extra solution I provided from Premtech helps clear that up. Cheers

  • Graeme Ross
    Graeme Ross Jun 30, 2008

    @midwest. the LA1460 is a low power dip chip... not a vertical output chip. What part of the circuit are you looking at?

  • Graeme Ross
    Graeme Ross Jun 30, 2008

    no problem glad to be of help. The chasis generally slide into rails on the front section, and also into the rear casing. It is not hard to manouver it about to get access to the verticlechip. They slide out and with not much "unhooking" of loom dress, you can turn the chassis over. Will post back to here tommorrow. Cheers

    regards
    robotek


  • Graeme Ross
    Graeme Ross Jul 01, 2008

    ----When the picture becomes a horizontal line, I can get the picture back by turning off the TV and
    turning back on after several minutes. It will then operate for 5 to 10 minutes before failing....

    Sounds like you are talking about an intermittent fault. This is classic behaviour for heat stressed dry/cracked solder joints about the VerticalOutput chip. The chip may even be desoldering itself from overheating in the first place, the conditions promoting the overheating being caused by failing overheated, vented out caps mounted near the heatsink.

    Have you got to the chassis yet?




  • Graeme Ross
    Graeme Ross Jul 01, 2008

    To help a little with the repair provess, I have found a link so you can download the service manual for the 32DF46. Is the 32 inch version of the set you have, but same chassis i believe. The LA7847 comes up for both models, so the vertical circuit will be relatively the same. It is marked as IC401,and is towards the center of the main board near the flyback (eht) transformer


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  • Toshiba Master
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The symptom is a vertical output problem (and has nothing to do with the tube itself). It is very common and is the result of some capacitors in the vertical circuit deteriorating with age. As long as you get it fixed before any active components fail (like the output IC) it is generally a $50 - $75 repair. If the output fails, then add another $25 - $50 to the repair. There is always the possibility that the IC has a thermal failure already, usually meaning a $75 - $100 repair; but the capacitors are the typical fault. Hope that helps..........

Posted on Jun 30, 2008

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Hi,

Often culprit would be the vertical IC. The are a fe instances that it could just be a resistor that has opened or increased its resistance.

Basic tools (DVM, soldering iron hand tools) should be enough. Perhaps you would not even need a service manual but a schematic would help.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.


Posted on Jun 30, 2008

  • Louie  Role
    Louie Role Jun 30, 2008

    Hi again,

    A bit of clarification pls, is your Toshiba a 27AF61 and additionally, would it have a chassis number possibly on a sticker either on the rear cover or on the aluminum heatsink near the flyback transformer.

    Looking forward to your postback.

    Cheers.


  • Louie  Role
    Louie Role Jun 30, 2008

    Based on your last post, then i am inclined to think that there is no component failure but rather a case of cold solder. Corrective procedure wold require re-application of heat with a soldering iron and perhaps a dab of soldering lead where required.

    robotek has given you a way of identifying the vertical IC.



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