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Toshiba TV - Inverter Transformer Arcing?

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    #1

    Toshiba TV - Inverter Transformer Arcing?

    Hi Guys,

    I've had a lot of luck so far in simply replacing caps in the PSU to repair monitors, and recently I put a generic inverter board into a monitor with no issues either.

    I just got hold of a 32" Toshiba TV that switches on for 2 seconds and then the backlights turn off, whilst the TV stays on.

    I've cracked it open, and I can see the invertor board. When this switches on - it makes a hell of a noise - almost like white noise - very loud. Then it stops when the back light turns off.

    I can't see any caps that look suspect - although there is one 450v 120uf on the main power board that looks like it's not quite flat - hard to tell.

    So I'm wondering - is there any repair that can be done to a transformer - or do I need to outright replace it, or the entire board? Could a cap further up the line cause the transformer noise (unclean electricity getting to it?)

    Any advice on the next step would be great.

    Spode
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    #2
    Re: Toshiba TV - Inverter Transformer Arcing?

    Originally posted by Spode View Post
    Any advice on the next step would be great.
    1) A model number would be helpful.

    2) Post clear focused pictures using the manage attachments button. Please do not post pictures inline as they slow down the loading of pages.

    For best picture quality and clarity take your boards to a window on a sunny day, turn flash off, and use macro mode. Take a top down view of all your boards (front and back). Make sure the photo is legible so that we can read the PCB printing clearly. A shutter speed of 1/125 or faster will produce nice clear focused pictures. Try to get a photo that is 2000x2000 resolution or as close as possible.

    Here is an example of the pictures we want.

    https://www.badcaps.net/forum/showpo...94&postcount=1
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    If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

    Please do not post inline and offsite as they slow down the loading of pages.

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      #3
      Re: Toshiba TV - Inverter Transformer Arcing?

      Hi retiredcaps,

      I was asking quite generic questions - which is why I didn't give model numbers etc. I want to understand possible reasons why I'd hear the noise I'm hearing.

      I did a bit more reading up and apparently this particular TV (Toshiba 32C3035D) quite commonly has failed inverter boards.

      My model uses a master and a slave unit. The slave unit is the one making the noise. If I unplug the power to the slave unit - it doesn't even try and start up. There's obviously some sort of protection mechanism in place.

      There are people selling repair kits for this board online - which comprises of 4 transistors and an IC chip - not the transformer.

      Looking more closely at the board today - one of the transistors looks like it has some mild burn marks. I'm thinking that perhaps it needs replacing, and I'm going to try and hunt one down.

      Question is - would/could that cause the arcing noise I'm hearing?

      If the IC was gone, I would have thought it wouldn't even turn on for 2 seconds. No?

      I've attached a couple of pictures - you can just about see the browning around the left hand transistor. Otherwise it looks quite helpful.
      Attached Files

      Comment

        #4
        Re: Toshiba TV - Inverter Transformer Arcing?

        Yes, bad transistors and usually the IC will die from it, that's a good reason the set is sold as a repair kit. replace those and all should be fine.

        Comment

          #5
          Re: Toshiba TV - Inverter Transformer Arcing?

          Cool. Never replaced an IC before. Any tips? From what I remember seeing before - it's a case of running the soldering iron over the pins with a bit of flux on there.

          I'll let you know how I get on. I paid £60 for the TV after making sure of the fault and no other damage - so all in all, £86, if the repair works.

          Comment

            #6
            Re: Toshiba TV - Inverter Transformer Arcing?

            Originally posted by Spode View Post
            Hi retiredcaps,

            I was asking quite generic questions - which is why I didn't give model numbers etc. I want to understand possible reasons why I'd hear the noise I'm hearing.
            The noise you are hearing could be from:

            an high voltage connection that not fully connected or bad connector

            an high voltage cable with an open isolation which it arcing to ground to some metal inside the case.

            bad high voltage transformer(s)

            an open CCFL backlamp(s)

            bad high voltage cap.

            hope this help
            ecking767

            Comment

              #7
              Re: Toshiba TV - Inverter Transformer Arcing?

              Originally posted by Spode View Post
              Cool. Never replaced an IC before. Any tips? From what I remember seeing before - it's a case of running the soldering iron over the pins with a bit of flux on there.
              Use of a de-soldering wick and flux will help. I use a vacuum de-soldering iron. Either will work, you can use a "solder sucker" but only try twice per hole or damage can occur.... really just takes practice and patience. When placing in the new one, I use a clip on style heat sink to the back of the ic to hold it in place and dissipate the heat from it as best as possible to solder it in without overheating the chip.

              Comment

                #8
                Re: Toshiba TV - Inverter Transformer Arcing?

                Well I managed to screw that up pretty badly. When desoldering the IC chip - most of the copper traces just flaked up and snapped off the board.

                I spent a lot of time repairing the broken traces using strands of copper wire - and for the traces that went under the chip, I had to solder on some wires and wrap them round to the back of the PCB. It took me FOREVER.

                The upshot of it, was that the master inverter switched on and powered it's side of the screen, and was no longer getting the signal to shut down (so something must have been working) - but the slave inverter wasn't powering up. I tried correcting my soldering, but no luck. It's tempting to have another go - but I'm at the point where I'm thinking of giving up this on PCB...

                From what I can see - both these inverter boards have a 72V input. Then there's a ribbon that goes into it, which by tracing the wires to the IC chip, I can see are for things like standby etc.

                I'm thinking that I might be able to get away with replacing it with a generic unit, but probably losing brightness options (not an issue).

                72V seems like an odd input voltage though - I have a feeling I'll struggle to get a unit?

                Comment

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