[BC] 4-400's

[Harveyesmith@aol.com]

Reply to Clay:

My experience with the 4-400's is that when they went flat, they were 
FLAT, sort of like a light bulb with the black spot inside the glass.

Too bad they would not rebuild these for a reasonable fee, as all 
they needed was more electron emitting coating on the filament 
(easily done if you are a glass blower mechanic.) and other begged to 
rebuild the glass WE and RCA glass envelope tubes.

I assume the reason they never tried to do it, simply was that they 
assumed these to be throwaway tubes.  I always felt the 833's and 
4-400, 4-1000 tubes probably could be rebuilt, but at the time the 
tubes were selling for under $100 (if they were not the 1,000's)

speaking of rebuilding tubes... I used to watch  Mr. Karnick up at HP 
hand make the oscilloscope tubes, he really was a craftsman... of 
course they (CRT's) are obsolete now and I believe he has passed away.

I once had him (on the side) replace the flood gun(s) in a variable 
persistence (very expensive) HP CRT for me.   turns out it (HP) used 
the filament off of a #47 pilot lamp (dipped into electron emitting 
juice of some type)  he popped it (the CRT) open, replaced the 
filament(s) and put it back together, evacuated it, and re-fired the 
getters, ( I always thought they were used up the first time, but 
learned different) and in a weekend I walked away with a fully 
functioning tube that would have cost $2500.

since he literally ran the crt operation at the plant, i never asked 
him where he worked on it, but he also had a full CRT construction 
operation at his residence (as he also built specials for the military)

oh well, all we have now is LCD's and they are throwaway also...

Harvey E. Smith
2020 Baculite Mesa Road
Pueblo, CO., 81001-2456