25VEZP22 color CRT

[radiotvnut]

That 1980 RCA console I just got uses a 25VEZP22 delta-gun tube. Just out of curiosity, I looked up that type in my tube substitution book and it list no subs. So, I wonder what is supposed to be so special about that tube?

During my used TV selling days, I did lots of tube swaps with other types that technically were not listed as a substitute. If the tube would physically fit in the set, if the gun structure was the same, if the yoke would fit properly on the neck, and if the socket was the same, then it would generally work.

As far as those late '70s RCA consoles that had somewhat lousy tubes, I've been known to stick Zenith Chromacolor II tubes in those (which was probably an improvement). The Sylvania black-faced jug was probably the best looking delta-gun tube from anybody, but those didn't always have a very long lifespan. The 1970s Zenith delta-gun jugs almost never die.

[Alex KL-1]

Years ago I got some CRT that I find tossed in dumpster. One "normal" 14", a flat 14", a flat 21" and a "normal" 20". All without yokes or purity rings. I started tests using a yoke fro the 20" model, and used for all other, with success (to diagnose). But all of this are normal modern in-line gun. Even without any rings, the 20" had acceptable convergence*** even for gamming, but the others, had defects besides the absence of rings (one unable to make any focus, other have dislodged mask, other I don't remember, I believe that had shorted gun).

***some end of CRT era (most 14" and 20") is knowed for not having any external ring.

I dunno about the convergence issues with delta gun CRT (mismatch or suchlike).

[JohnCT]

Originally Posted by radiotvnut

I looked up that type in my tube substitution book and it list no subs. So, I wonder what is supposed to be so special about that tube?

Possibly nothing, that tube number might have just slipped through the cracks when sub books were written.

There could also be a difference in the mounting - RCAs used both a removable compression band and four "ears" or sometimes the safety band was factory installed in later tubes.

RCA also went to tinted phosphors with the ColorTrak and maybe there was a difference in that regard.

But yes, I used to swap tubes all the time, including some black and whites in the 1970s that even had a slightly different shaped face plate. Some socket changes or rewiring would get a perfect picture out of them. Back then, people would pay good money even for a black and white TV.

That tube you have could have had a minor peculiarity to it that would be no problem with a swap, but wasn't *technically* directly swapable.

John