"Jim Lesurf" wrote in message

In article , Patrick Turner
wrote:



And I am only one of maybe 50 repair blokes in a town of 300,000
ppl.

Says something good about the actual reliability of modern
electronic components.

There shouldn't be a single failure of an SS amp in my town in any
given year.

How many commercial valve amp designs can you quote reliability
statistics for that show failure rates of 1:300,000 or less per
working year?

The other half of the story is the genesis of the missile defense system
that I worked on in the Vietnam era. Interesting because it is still in
service today. An apples-to-apples comparison is possible. When I worked on
it, a Hawk system was composed of about 10 major functional units, each
barely small enough for highway travel. It was powered by about 8 45 KW
diesel generators. With full complement of staff it took about 100 men and
35 duce-and-a-half trucks to move. At least 5 of the 10 functional units had
MTBFs on the order of a day or less. Each was tuned and thoroughly checked
several times a day. The rest were only a bit more reliable. Three of them
had about 400 tubes each. Just the cables required to tie this system
together weighed over a ton.

Today, the fire control system fits on the back of a Humvee which also
powers it. It has about 5 times the range. None of the equipment is
routinely maintained in the same sense. Components basically run until they
break (rare) or are fired, and then they are replaced.

Really and truely the only difference is solid state technology and other
technological changes that it enabled.