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32zp48 buzzing

Discussion in 'Televisions' started by flakey, Nov 4, 2004.

  1. flakey

    flakey
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    After lurking on these boards for a while I decided to buy a Toshiba 32zp48. The geometry on the one I got was out by over 10 mill so Toshiba replaced it about three weeks ago. The second one was OK until tonight when my wife decided to check what was on TV with the TV guide on Sky. It was then we heard a buzzing coming from inside the TV - not the speakers. She regularly checks the sky TV guide and the buzzing has only just started tonight. More investigation shows that the buzzing changes tone and volume with different camera shots on any TV channel either through sky or just the TV. Playing a DVD is OK though. I have the sky box on ext1 with a profigold scart lead, video on ext2 with a profigold scart lead and pioneer DV575 on composite/optical audio on ext4. Is there an explanation for this buzzing? Leaving the TV off for a few minutes doesn't help. TIA.
     
  2. red16v

    red16v
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    I'm disappointed to hear that anyone has a faulty 32ZP48 - I think it's a great set (I have one myself and regularly recommend it on this forum). Difficult to tell at a distance, but from what you are describing the cause of the fault is that as the crt picture content changes so the current taken by the electron beams change and so the load on the tv set ht/eht stages changes. This is all quite normal. However, sometimes, over time, components (transformers or coils) which involve the use of tightly wound coils of wire can develop a problem whereby the tighly wound coils of wire loosen up. What happens then is that the coils can then 'vibrate' due to the high currents passing through them. As the 'current' demand changes through them so the frequency and amplitude of the vibration alters - I think its very likely that's what you're suffering from and that's what you can hear. It's not a fault - but it can be very annoying in a domestic environment. There is little that you can do as I assume you are not an electronics expert? The usual solution adopted by any competent tv engineer would be to take the back of the tv set and using the blunt end of a long insulated instrument (ie, a wooden pencil) and poke around the various transformers and coils inside until you detect that poking one particular component stops the noise. Normal practice would be to replace that component or if the duff component's wound coils can actually be seen sometimes splashing an amount of bathroom type sealant over the coils will dampen down the vibrations. I'm sorry if the practical solution is not helpful since I do not recommend you go anywhere the back of the tv set if you are not qualified (and that's not the same thing as being gung-ho or over confident, you could cause severe harm to yourself) If the tv set is still under warranty ask that it is taken away and repaired. regards, yt
     
  3. flakey

    flakey
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    Thanks for the reply. Further investigation showed that the buzzing is more prominent when I bring up an on screen menu either in sky or on the TV itself to change contrast etc although this morning it's not as bad. Possibly a heat related problem when the TV has been on a while. I'll see how it goes over the weekend when it's on most of the day.
     
  4. red16v

    red16v
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    Ah, bringing up a menu usually implies bring up a large solid area of high brightness - the electron beams take more, hence more noise. Wouldn't be at all surprised if it's heat/time related - it usually is. regards, yt.
     
  5. davidly

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    In my experience this "buzzing" is caused by the velocity modulation drive coil. The 32ZP38 (for example) appears to have differing levels of vm depending upon which picture preset is in use (or has been modified and saved as m). On my 32zp38 the rather overprocessed preset 1 has the most vm and hence audible noise, the softer looking preset 3 the least.
    Imho some velocity modulation is required - but not too much as it can lead to rather artificial looking edges and other nastys. I personally use preset 2 as a basis for picture settings.Hope this is of some help!​
     

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