The timers in commercial amps I've owned all prevent the T-R relay from
engaging, thus preventing drive to the tube(s). They don't key the B+ in
any way.
In my homebrew ceramic-tube amps using tetrodes (4CX250s, and lots of them),
I always derived screen voltage from plate voltage, so if the B+ failed, the
Eg2 would disappear just as quickly, but always had all operating voltages
turn on and off with the heaters. I'd use a timer only on the T-R relay.
The amps I built in 1980 are still working with the same tubes in them after
all these years....through thousands of on/off cycles. Maybe the "big"
tubes are different.
-WB2WIK/6
Correct me if I'm wrong, but doesn't the HV come up almost instantly after
the amp is turned on? I use GLASS tubes, so I'm not an expert on these
fancy ceramics, but I think the delay circuit keeps the amp from being keyed
so it can't be driven until the timer expires. Or is the HV off until the
timer expires, too?? That's why I like my graphite 3-500Zs -- 4KV @ 1A with
nearly instant warmup and easy 2kW output. And less than $300 for two...
BTW, what exactly *WAS* the definition or "is"?? :-)
Joe,
N3JI
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