Another 10BP4 on ebay...
 

Yet another 'extremely rare' 10BP4 on ebay. This one's not new in box. These things pop up constantly, it seems.

Ok - so, big question - how come there are zillions of these things *still* floating around? I've seen plenty of unused 10BP4s, a good number of them new in box. Did RCA overproduce, not anticipating a shift towards larger screens that happened relatively quickly? And, weirdly - it was listed as in production even into the late 50's, in RCA's tube manual.

Wha'ts the story on them?

Some wild theories I came up with:
1) they are fairly small so they were easy to stash away in the attic or the back room, and survived.

2) early tv repairmen were not always that smart and so often bought new crt's when they didn't really need them

3) it took some time for repair shops, dealers, distributors & manufacturers to figure out just how long picture tubes would last in the real world & how fast they would sell, so they stocked up on them

I'll go with the third opinion..
 

For some time, it was supposed that crt's would only last maybe 3 years or so, in a tv. I have an article on color tv, from 1963 in a magazine called "practical electronics(NOT the UK version), and the author stated that, if a color crt lasts the first six months, it would probably go on to give a good picture for its normal lifespan of about THREE YEARS!!(what a laugh) ALL of us have seen a LOT of crt's that seem to last FOREVER!! If they only did last three years or so, we would NEVER find an old tv, with a good tube(Perhaps he was looking into the future, to the '91 to '99 Zenith crts, that REALLY did only last about three years before shorting out, and KILLING the main Pc board!)