8877 HV can be safely applied during any period of the start up (initiation)
cycle without consequences. However, it's positively essential to series
install a 180 second (NO) delay relay in the antenna changeover circuit to
inadvertently prevent the premature application of audio excitation prior to
meeting minimum factory heater warmup parameters.. If available, additional
(unused) delay relay contacts can be utilized for warmup,standby, and delay
satisfaction neons. Ron W2CQM/3
---------- Original Message ----------
amps@contesting.com>
To: Jim Barber <barberaudio@gmail.com>, Amps group <amps@contesting.com>
Subject: Re: [Amps] 8877 - HV with heater, or later?
Date: Mon, 23 Jan 2023 17:56:49 +0000 (UTC)
The 3cx800 tubes are in the same class of tube as the 8877 and no ham amplifier
using it holds of the plate voltage. Same goes for 8877 except for the the
Ameritron AL1500. s long as the cathode does not see drive until warmed up
that’s the only requirement. K don’t think Eimac even suggests
holding g of plate voltage but of course that are definite about no drive power
being applied. I suppose if you hold off the HV it could be considered an
extra precaution measure.
Sent from the all new AOL app for iOS
On Monday, January 23, 2023, 12:26 PM, Jim Barber <barberaudio@gmail.com> wrote:
I'm overhauling a vintage 8877 amp, and it occurs to me that I've never
seen a definitive answer to this question:
Should HV be held off on a 8877 until the heater warm-up timer expires?
Not that I claim any particularly deep or insightful knowledge of such
things, but it seems to me that if the cathode has cutoff bias that it
wouldn't make any difference when B+ is applied.
I did find a reference to this question in the amps archives, but every
design I've looked at recently holds the HV off until the cathode is ready
to go.
Maybe there's more to it than I'm seeing? I may use a separate HV switch on
the front panel anyway just to allow for gettering, but I'd still like a
consensus on the question.
Thanks!
Jim N7CXI
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|