Relay computerswhy so few 14

I don't have an RCA recieving tube manual handy, but IIRC, the typical low level 6 volt filiment tube was on the order of .125 amps. UNIVAC used 25L6s (I think), which were 25V filiment (thus 5 in series = 125V), lower current, but also a tube not intended for high frequency orlow level work (it existed as a power amplifier for radio speakers, and not a very good one at that). Realize - in the late 40's, there was still a big tube shortage out there, plus a LOT of new types hitting the market. It was not uncommon to see radio and even TV sets that would start a production run and change a few tube types 1-2way through, even going from octal to minatures (the 6AQ5 was designed as a miniature 6V6 replacement - RCA used the tube into the 70's).

Oh yes :)

I suspect they did, but not as severe - something ventilation could tackle.

far far slower.

Noisy, too.

Questionable. Tubes got really reliable after the war - low signal types in particular tended to last a LONG time, if not driven to their limits. "Power" types, such as audio amplifier output tubes, never were really reliable. Low level tubes would often fail from going noisy or microphonic.

One big help was to hold the high voltage off until the tube was warmed up - this prevented a lot of Bad Things(tm) and kept the life up.

Not always. They tended to get noisy or slowly die off, too. filiment burnouts are rather uncommon, actually.

True. but relays could do bad things - intermittents, etc.

Capacitors were a BIG problem in electronics - in fact, they were generally LESS reliable than tubes.

Among other things. The industry ultimately developed a few types that were specifically designed for computer use.

Then again, early transistors weren't amazingly great either - lots of people have 'lasts forever' transistor radios from the late 50's that won't work because of dead semiconductors. And they're generally HARDER to find replacements for!