Ian White G/GM3SEK wrote:
> Gary Schafer wrote:
>
>>
>>
>> Ian White G/GM3SEK wrote:
>>
>>> Phil Clements wrote:
>>>
>>>>>> I believe I've read on here before where some owners have built
>>>>>> MONO band
>>>>>
>>>>>
>>>>> amps but powered them all from a single power supply. So, one power
>>>>> supply deck and TWO RF decks. It has been suggested that I use vacuum
>>>>> relays to switch between the two RF decks. I was hoping to have
>>>>> them both
>>>>> run in standby at the same time. I obviously do not know enough
>>>>> and am
>>>>> therefore here seeking guidance. I will only operate one amp at a
>>>>> time.
>>>>
>>>>
>>>> Frank Donovan, W3LPL is probably the world's best source of info on
>>>> this type of lash-up. His multi-multi contest station, as I recall,
>>>> had amps for each band, with only one power supply. It may still be
>>>> in operation.
>>>>
>>>> No, you don't need any relays to switch HV; just excite the amp you
>>>> want to use. I would highly recommend HV glitch resistors in each RF
>>>> deck, and also in the power supply.
>>>>
>>> A separate resistor in each amp would reduce interaction and voltage
>>> drop, but a resistor is needed in the power supply as well, to handle
>>> the situation where one of the B+ leads shorts to ground.
>>> Each amp also needs its own separate anode and grid current
>>> metering. A Triode Boards customer is looking at this right now, and
>>> I think I've second-guessed how Frank must have done it, with
>>> isolating diodes in the B-minus return.
>>>
>> What about if you don't light the filament on each amp?
>
>
> Workable for a single station, and for directly heated tubes; but in a
> multi-multi station, each amp needs full real-time metering.
>
I should have posed the question differently. What I was really asking
was: What about applying high voltage to a tube when the filament is not
powered up? Isn't that harmful to the tube?
73
Gary K4FMX
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