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Interesting faulty 1 year old CRT (really dim)

Discussion in 'Electronic Repair' started by Jason D., Jan 16, 2004.

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  1. Jason D.

    Jason D. Guest

    Got bad tube that didn't do anything like arcing, shorts or bright pix
    with retrace lines, new tube not typical dim tube of a worn out tube
    and chassis is still happy as clam. In fact measured all the voltages
    (including G2 up to 500V on dmm) and were all correct except cathodes
    volts were low but not too unusual (appox 90~120V) Even the HV is
    right on. Yet set is too dim to watch even with user brightness
    cranked up. Focus made the convergence change bit too much.

    Scratched head for awhile and looked, looked then decided chassis swap
    to another set with good CRT (RCA made even was rebranded) CRT for any
    makes with same part number will work). The problem didn't move with
    chassis and got perfect picture, cathodes all went up to correct

    What up with that dud tube? Was only bit over year old and tube is in
    recent JVC set (AV-27D303).

    Curious & Cheers,

  2. Gassy, the tube is soft, usually an air leak past the pins. This is a
    rare problem but does happen if the tube is of defective manufacture
    or has received a bump bad enough to cause the pin connector to crack
    the glass around the pins. The low Cathode voltages suggest abnormal
    beam current.. You may eventually get a arcing or flashing in the
    tube and the neck may glow blue. (In fact look for this now) I had
    this once where I managed to scratch and I guess crack the the neck of
    a fairly new tube when changing the yoke.

    . Steve .
  3. GPG

    GPG Guest

    POss o/c A1. Have seen o/c g1 in a near new tube, failed weld.
  4. David

    David Guest

    Tube should be under warranty for almost another year. Unless JVC like many
    other cut back the crt warranty to only one year.
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