12LP4 post mortem

[jeyurkon]

Originally Posted by jr_tech

Wow! What happened to the heater...all that I have ever seen are a "double helix looking" design. Did it just fall apart when you pulled it out or was it really deformed during processing somehow?

(please pardon the crummy scan)

jr

I wish I knew. It was that way before I pulled it out though. Because it was so deformed it wouldn't slide out easily and that's why the leads broke off.

John

[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

[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

[Bill Cahill]

The gun in my dud 10BP4 in my Bendix tv has an interesting look.
The part of the gun closest to the filament is black. The other part in front is a bluish yellow.
Is this from shorts, or, burn out. ? Filament still lights.
Bill Cahill

[jeyurkon]

I can only guess. It sounds like it is gassy, but not up to air. The color is probably due to an oxide layer. The thinner layers produce vivid colors by interference. When it gets thick it just looks black. The part by the filament would get the hottest and have the thickest layer.

Is part of the phosphor on the screen missing or is there a burn in the screen? If the screen had a bad burn from losing the vertical scan it could produce gasses including sulphur.

John