Beko 21241tds - crt

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  • tmcw
    Badcaps Veteran
    • Oct 2010
    • 382
    • Ireland
    #1

    Beko 21241tds - crt

    Just thought I'd run through a couple of issues I'm experiencing with this set.

    The first issue is with a whining, high pitched noise the TV makes a short time after startup. After a couple of minutes, it begins to make a high pitched squeal, then gets a little higher in pitch, and then suddenly the squeal just dissolves away (I liken it to the way a headache disappears 10-20 minutes after taking a couple of Neurofen).

    Now, I had the back cover off earlier, and it seemed that the noise is there a few seconds after switching on, I just didn't hear it before, the cover must shield some of the earlier pitch noise. Anyway, I had a screwdriver, and flexed the board in the area in the photographs attached, and the noise would come and go. Interestingly, as I moved the screwdriver towards the component marked "termal 70u" the pitch got higher, even though I didn't touch it. And as soon as the screwdriver touched the component, the squealing stopped; lift the screwdriver and the squeal would return. Touching a few other small components around there seemed to muffle the squeal as well. Top of that component is magnetic too; anyone know what it is? It has a coil around it.

    So, anything I can do to stop the squeal? Do I need to resolder the other side, it's legs look like they could do with a bit more? Does this component get hot? Needs to be replaced?


    The other issue is with some of the TV adjustments, namely colour and sharpness. When I try to adjust them, the adjustment doesn't do anything to the picture, the scale moves all the way from 0-100, but no difference to picture. The range of the brightness and contrast seems like they could be better too, but there is a noticeable change when they are adjusted. Volume adjustment seems to be ok. Anyone know what's likely to be at fault? I've attached a photo of the AV area, but there doesn't seem to be much to it, a number of caps and a few chips mainly. I can make a better photo if anyone thinks it would help. The picture on the set is pretty good, for a TV of this age, but a little bit of colour would improve it quite a bit. Would old caps affect issues such as this?
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    • Th3_uN1Qu3
      Believe in
      • Jul 2010
      • 6031
      • Romania
      #2
      Re: Beko 21241tds - crt

      For the adjustments, more likely resistors that have shifted value or bad solder joints.

      The whine is coming from the flyback (loose windings) and unfortunately there isn't much you can do about it.
      Originally posted by PeteS in CA
      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
      A working TV? How boring!

        Comment

        • dumpystig
          Badcaps Veteran
          • Jul 2011
          • 485
          • UK
          #3
          Re: Beko 21241tds - crt

          First off get your vacuum out and get rid of all the dust and crap that's built up. The component you refer to is an inductor/choke; try resoldering the joints, then apply several drops of superglue along the top of the coil windings, letting it soak around the coil aided by gravity - let it dry then repeat 2 or 3 more times. This worked for me when I recently repaired the PSU in my LCD TV, although the noise wasn't as bad as what you seem to be experiencing. Good luck
          System: HP xw6600 Workstation, 650W PSU | 2x Intel Xeon Quad E5440 @2.83GHz | 8x 1GB FB-DDR2 @ 667MHz | Kingston/Intel X25-M 160GB SSD | 2x 1TB Spinpoint F3, RAID0 | 1x 1TB Spinpoint F3, backup | ATI FireGL V7700 512MB | Sony Optiarc DVD +/-RW | Win 7 Ultimate x64 | 2x Dell UltraSharp U2410f | Dell E248WFP

            Comment

            • tmcw
              Badcaps Veteran
              • Oct 2010
              • 382
              • Ireland
              #4
              Re: Beko 21241tds - crt

              Thanks for the pointers.

              Resoldering the legs of the inductor seems to have sorted that issue. I'm guessing it didn't have enough "foundation", and as it warmed up, was able to vibrate at various frequencies. I added a nice blob to each leg and it seems to have stopped, so hopefully that issue is sorted.

              Funnily enough, the adjustment issue of colour and sharpness seems to have been sorted too, although all I did was unsolder and test one resistor (the one beside the tuner), as in circuit it didn't have the correct resistance, but out of circuit it did. I cleaned the board a bit too, there seemed a bit of reside of a spill or where liquid had entered around the area of the SCART and aerial sockets. How would doing those have improved the adjustments?

              The brightness and contrast seem to have more of a range too. Fail to see how cleaning the board may have helped, but maybe it did.

                Comment

                • dumpystig
                  Badcaps Veteran
                  • Jul 2011
                  • 485
                  • UK
                  #5
                  Re: Beko 21241tds - crt

                  It's amazing when you think you haven't really 'done' anything yet you seem to have achieved a result! The resistor measurement in-circuit may have been affected by other components, or it may have been a bad/dry joint, which could explain a fix after it being resoldered. You also noticed the bad inductor joints - these circuits generate a lot of heat which creates bad/dry joints, especially on high current components. I hope your fix is long lived.
                  Last edited by dumpystig; 07-09-2011, 11:55 AM.
                  System: HP xw6600 Workstation, 650W PSU | 2x Intel Xeon Quad E5440 @2.83GHz | 8x 1GB FB-DDR2 @ 667MHz | Kingston/Intel X25-M 160GB SSD | 2x 1TB Spinpoint F3, RAID0 | 1x 1TB Spinpoint F3, backup | ATI FireGL V7700 512MB | Sony Optiarc DVD +/-RW | Win 7 Ultimate x64 | 2x Dell UltraSharp U2410f | Dell E248WFP

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