Interesting faulty 1 year old CRT (really dim)

[Jason D.]

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
values.

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

Curious & Cheers,

Wizard

 

[Steve(JazzHunter)]

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
values.

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

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 .

 

[GPG]

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 .

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

 

[David]

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