12LP4 post mortem

[jeyurkon]

Originally Posted by jr_tech

I have seen a few that have developed H-K shorts where the heater has "welded" itself to the inside of the cathode nickle, and have been very difficult to remove without distorting/breaking... did this crt have a H-K short? Most of the heaters that I have seen after years of service look pretty much like the picture that I posted above, although they may "darken" somewhat over the life of the tube.

jr

I sent two tubes to Scotty for rebuild and I don't know which gun he sent back to me. One of them did have a heater/cathode short and a G1 short. The other only a G1 short. It could have been this one. It appears that this heater/cathode was severly overheated. That could have been from a brightener, or if turns of the heater had shorted, that could have caused the overheating also.

The 10MP4 in my Sylvania is orginal. The striking thing I notice about it is that's its heater is a very dull cherry red. Not nearly the amost white that I see in other CRTs. I wonder if that's contributed to its longevity. It still performs very well.

John