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hv sparking problem

Discussion in 'Electronic Repair' started by [email protected], Aug 22, 2006.

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  1. Guest

    I am working on a Toshiba 32hf72 chassis N2PS. Found a bad flyback and
    replaced it. Now there is a problem with the HV sparking. At first it
    sparked around the anode connector. I cleaned that with no effect. I
    have found a couple things that don't make sense to me:

    Connected the HV to another tube and connecting the dag together with
    no other connections yield proper start up with no sparking.
    Connecting the tv together normally, but using a different yoke that is
    not on the tube makes the tv start up, but it sound wrong. there is a
    sound like sizzling inside the tube. Hard to describe. if the yoke on
    the tube is connected instead of the other yoke, I get sparking again.
    ANY ideas?
     
  2. Bad CRT? Air in CRT?
     
  3. Guest

    I dont know what specifically you cleaned, but I know that any arcing
    converts anything present to carbon, and any cleanup has to be very
    thorough indeed to work.

    If youve replaced the EHT wire/rubber cap and cleaned everything
    immaculately, the only remaining culprit would be the CRT, if thats
    where the sound is coming from. Dont think I've encountered a tube
    doing that before, but if it is, it is.


    NT
     
  4. JW

    JW Guest

    Power up the monitor while in the dark - you should then be able to locate
    where the arc is occurring from and work from there. If it's coming from
    where the cap meets the tube, try using RTV to seal the connection.
     
  5. Guest

    I cleaned the anode cap and the tube where it attaches. I experimented
    a little more and found that the sparking happens when the horizontal
    half of the yolk is connected, but using the horizontal section from
    another yolk, I get a dot in the middle of the screen, so the tube
    works at least a bit. Can I assume that if i get a dot, then the tube
    is fine or could there still be a problem with the tube?

    could a problem in the ABL circuit cause these results? I suspect
    there may be one because I found some blown resistors.
     
  6. Guest

    definatly coming from under the cap. Is it possible the HV is WAY to
    high? if so and I manage to seal it, would this cause problems?
     
  7. Art

    Art Guest

    ??Have you checked the operating B+ voltage, and the HV ?? Check the inside
    of the anode cup to see if there are any carbon tracks that have built up,
    if so you may need to replace the actual suction cup assembly for another
    fly, such as the original one. Is the number on the new flyback the same as
    the original? Does the neck of the CRT glow a strange bluish colour when
    the arcing occurs?
     
  8. Of course it can do harm to you and the TV.

    But first clean the area again and lift the rubber suction cap away from
    the tube so that any carbon tracks on it aren't an issue. See if it powers
    up without sparks.

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  9. Guest

    These 2 paras appear to contradict each other, so I can only say I dont
    know whats happening. As you didnt replace the rubber cap and lead,
    really its hard to conclude much.

    ABL? whats that?


    NT
     
  10. Guest

    auto beam limiter.
     
  11. Guest

    no connection


    NT
     
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