"Wiebe Cazemier" wrote in message
b.home.nl...
On Monday 28 April 2008 14:11, Wiebe Cazemier wrote:

I have the monitor running now without the blue gun connected. The fault
persists. When I turned it on, the screen flashed blue on and off like a
stroboscope. I was able to reproduce it by tapping the neckboard. Now
that
it's warm, the fault is gone again.

Whoops, I meant, with the blue gun disconnected...


There is one difference. Before, the screen would contract and expand and
eventually turn off when it did this, probably because the CRT driver (an
LM2413 BTW) was shorted to ground through the blue cathode.

Anyway, the fault seems to be in the tube, in the blue gun. I will try
the
shaking method a bit more, and hopefully I don't have to take any drastic
measures. BTW, I read somewhere in one of the sci.repair faqs that you
have
to tap the neck quite hard: "not enough to break it, but close". I don't
really dare to do that...


Yep, sounds like it really is the tube. If it's a heater-cathode short, you
could isolate the heater, powering it with 2 or 3 turns of wire around the
flyback core. Careful not to overdo it, it really only takes a couple of
turns on these high frequency transformers.