if that often. Even our least reliable tubes were good for a month or two.

When we had to replace tubes, each section was separately powered, so we could shut them down individually. And attempting to replace a tube without removing power from the system either got you a reputation as the electronics tech equivalent to "script kiddie" or a very nice wake at which your former co-workers consumed mass quantities and stood around shaking their heads and saying "What an idjit."

I serviced domestic radios etc thru the war capacitors and resistors were the biggest problem and the resistor problem was not really solved till the seventies, the introduction of all glass valve's introduced a new problem with poor contacts with the sockets (Russian ones were best with gold plated pins) with the all too familiar problem of having to bang the TV to make it work.

As those of us who once repaired granny's wireless set will know, the high voltage was a problem not so much for the valves as for the passive components. Insulating materials were not nearly as good as today, and they were usually based on shellac. Part of the skill of good design was ensuring that a fault such as a short-circuited blocking capacitor didn't take a cascade of valves with it. Draw grid current and the valve will soon be dead, and valves weren't cheap.

Mains transformers with 350-0-350 V secondaries would often go up in smoke.

I remember when working in medical research during the 1970s having to resurrect some old radioactivity counting gear. It had hundreds of valves, and of course those impressive power supplies. There was also a mercury delay line, presumably of the same design as the ones in the early computers.

if that often. Even our least reliable tubes were good for a month or two.

When we had to replace tubes, each section was separately powered, so we could shut them down individually. And attempting to replace a tube without removing power from the system either got you a reputation as the electronics tech equivalent to "script kiddie" or a very nice wake at which your former co-workers consumed mass quantities and stood around shaking their heads and saying "What an idjit."