On Friday 02 May 2008 03:44, John-Del wrote:

You can't clear a heater to cathode short, no matter what you do. No
commercial CRT restorer even attempts it. If you try to discharge a
current through the short, you will kill the filament. The only
solution is to provice a "floating" heater source that won't drag the
cathode low when the contact is made. The heater voltage will
actually rise to cathode voltage (above ground), but will remain 6.3
between the filament pins. One method is to buy an isolation
transformer from supply houses, which is basically a toroid with two
windings on it. The other is to manually wrap some wire around the
flyback core, and feed to the filament. In either case, the CRT board
must be modified to float the filament pins completely away from
ground. Very common procedure done at repair shops.

Hmm, there seems to be some disagreement over whether a H-K short can be fixed.
Will the filament also be killed if you tie its pins together? That way, a
current path other than through the entire filament always exists.

Floating might work, but not in this case, because the problem exists in two
guns. Additionally, it would decrease image quality (at least when the short
exists; it might clear up when the short disappears when it's warm), and the
reason I want to fix this monitor is because of it's high quality; a quality
that not even other T766 models have/had.

Another thing; if I measure the filament voltage, it's 5V. Is that normal
deviation from the 6.3 which is common? And, when isolating, is it useful to
use some kind of regulation, like with a couple of diodes and an LM317, to
make sure the voltage is exactly what it should be?