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

[Victor Rosenthal]

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

https://frank.pocnet.net/sheets/140/8/8877.pdf

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

https://frank.pocnet.net/sheets/140/8/8168.pdf

73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/

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
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