[Amps] 8877 - HV with heater, or later?

Victor Rosenthal k2vco.vic at gmail.com
Mon Jan 23 14:35:42 EST 2023

Interesting that the 8877 datasheet gives a warmup time of 90 seconds, 
but doesn't say whether you can apply plate voltage.


On the other hand, the 4CX1000A datasheet explicitly says that no other 
voltages should be applied during the warmup period.


Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5

On 23/01/2023 19:26, Jim Barber 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 at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps

More information about the Amps mailing list