Nice stories below. Credible. Thanks. I have a few comments below.

On Sun, 6 Apr 2008, COLIN LAMB wrote:

My Collins KWM-2 uses a home brew power supply. Step start on filaments -
at correct voltage and no high voltage for 60 seconds. Same tubes in it for
30 years. I think the only two power amplifier tubes that failed were
dropped on the floor. Some amplifiers adjusted the filament voltage to be
correct and some were never measured.

Out of many dozens of tubes in ham gear, I think I never lost one by any
failure mode. I found an old Halicrafters S-85 at a hamfest and bought it
out of nostalgia. Has original tubes (all marked Halicrafters).

Our B&W TV sets (when I was a kid), however, had maybe half a dozen tubes
go soft and needed replacing. I've bought a number of ac-dc AM/FM radios
with tubes at hamfests and still have original tubes and still work!
Vintage 1950s.

I ran a 3 x 813 amp for years and never changed the tubes or even measured
the filament voltage. Just used a transformer with the rated voltage and
called it good. Unless the filament transformer has a current rating much
higher than the demands of the amplifier tubes, the surge will probably be
ok.

Incidently, the home brew equipment looks practical. I built a vfo using
the Collins 70H3. The problem with it is that it covers 1.5 to 3 MHz with
10 turns. That is 150 kHz per turn. Bad for a linear dial.

Yeah, I know. So, I use gears and don't worry about more than couple kc
accuracy. I'm not a Digital readout freak.

I bought a couple of R-390 VFOs from Fair Radio Sales (Lima, Ohio). Out of
three I bought, two worked and they are something like 2.4 to 3.4 mHz, and
so 100 kc/turn (ten turns nominal, twelve turns real, and still linear,
they go actually up to 3.6 so can use directly on CW part of 80 meters).

I used a 8:1
reduction gear and a crystal controlled mixer to cover 5 to 6.5 MHz, then
limited use to 5 - 5.5 MHz. That was coupled in as the second vfo for my
Drake TR-5, so when I switch it in, the Drake digital dial displays the
frequency. Extremely stable. Oh, I converted it to solid state, also,
which is easy to do. There is one minor problem in that there are no stops
on the dial. Not a problem for me, but if some kid came in and started
twisting, he could break something. Oh well, you need to take some risks in
life.

make your own stops.

73
W4PON

73, Colin K7FM