Everything was working fine...then one day, TV stopped working. I
checked the circuit. Q404 was blown. Changed it. Turned the power
ON, it blew again - stupid me. After checking for other shorts, took
out all the CRT tube connections from ditstribution block. Changed
Q404. Nothing blew. Put in red tube, no problem. Connected blue
tube, no problem. Connected green tube, Q404 is shorted. Took out
green tube, changed Q404. TV worked fine. Picture is messed up as
green is missing but the video and audio otherwise is good.

Checked green yokes (how do you check them?) by switching them with
blue one (I always kept the green tube disconnected). No problems. So
that means yokes are fine, right? May be the distribution block has a
problem and can handle only two tubes at a time. Took out blue one and
only connected red and green. Same problem - blew Q404. Gave the
boards (only the signal board and the power board) to a friend. Who
hooked them up at his shop and said everything is working fine. The
only thing to do is to replace the green tube. Ordered one. Replaced
it. Turned the power on and the Q404 got shorted! By now, my supplier
is running out of Q404! And I am running out of ideas to test. So I
seek help. Obviously, there is something about green tube - are you
supposed to do something to the tube before you connect it?

What can be the problem? How do I test for it? What am I doing wrong?
Any help is appreciated.
Thanks

junglee

Shorted Green CRT.
"junglee" wrote in message
ups.com...
Everything was working fine...then one day, TV stopped working. I
checked the circuit. Q404 was blown. Changed it. Turned the power
ON, it blew again - stupid me. After checking for other shorts, took
out all the CRT tube connections from ditstribution block. Changed
Q404. Nothing blew. Put in red tube, no problem. Connected blue
tube, no problem. Connected green tube, Q404 is shorted. Took out
green tube, changed Q404. TV worked fine. Picture is messed up as
green is missing but the video and audio otherwise is good.

Checked green yokes (how do you check them?) by switching them with
blue one (I always kept the green tube disconnected). No problems. So
that means yokes are fine, right? May be the distribution block has a
problem and can handle only two tubes at a time. Took out blue one and
only connected red and green. Same problem - blew Q404. Gave the
boards (only the signal board and the power board) to a friend. Who
hooked them up at his shop and said everything is working fine. The
only thing to do is to replace the green tube. Ordered one. Replaced
it. Turned the power on and the Q404 got shorted! By now, my supplier
is running out of Q404! And I am running out of ideas to test. So I
seek help. Obviously, there is something about green tube - are you
supposed to do something to the tube before you connect it?

What can be the problem? How do I test for it? What am I doing wrong?
Any help is appreciated.
Thanks

junglee

I agree with you that it looks like a shorted green CRT. But I just
bought a new CRT! Did I do something to short it? How can I test for
this short?
Thanks for your help.

junglee

Sounds like the new tube did not get the new hv lead properly attached
and sealed to the tube and allowed to cure a minimum of 24 hours before
applying HV.

junglee wrote:
I agree with you that it looks like a shorted green CRT. But I just
bought a new CRT! Did I do something to short it? How can I test
for
this short?
Thanks for your help.

junglee

David,

You are correct as always! (I have been watching this news group and am
really impressed with your insights!) I did not do what you just
described. I did not allow 24 hours for curing. Now the main question
I have is - did I ruin the CRT? I am going to seal the hv lead and
allow it to cure for 24 hours. Is there anyway for me to test the CRT?
Is it too late?
Thanks.

junglee

wrote:
Sounds like the new tube did not get the new hv lead properly
attached
and sealed to the tube and allowed to cure a minimum of 24 hours
before
applying HV.

Need to remove the anode lead, clean the connection thoroughly, looking for
any carbon tracing on the outside of the glass envelope. Re-attach the anode
lead with sufficient sealant and let cure 24+ hours. If the carbon track has
been removed and the seal done properly you should have an operational
device. Actually the only way to check that is to subject it to the
application of operational voltages and currents.
"junglee" wrote in message
oups.com...
David,

You are correct as always! (I have been watching this news group and am
really impressed with your insights!) I did not do what you just
described. I did not allow 24 hours for curing. Now the main question
I have is - did I ruin the CRT? I am going to seal the hv lead and
allow it to cure for 24 hours. Is there anyway for me to test the CRT?
Is it too late?
Thanks.

junglee

wrote:
Sounds like the new tube did not get the new hv lead properly
attached
and sealed to the tube and allowed to cure a minimum of 24 hours
before
applying HV.