>
>
>.
>> Eimac does not say anything about limiting the startup current to the
>> 8877 heater. While it is true that directly-heated cathode tubes have
>> about 8.3-times less filament R at startup, the heater of indirectly
>> heated cathodes does not exhibit a large R decrease when cold.
>>
>> cheers
>>
>The question was about a 3CX1200A7, I thought.
>Measurements have shown that inrush on the heater of this series tube
>can exceed the limit,
There is no stated inrush limit for the 3CX1200A7 filament.. The
3CX1200A7 does not have a heater.
> especially if the filament transformer is more robust
>than the required current rating of the heater(s) it is powering.
>Also, the guys turn their amps on and off thousands of times more in the
>life of the tube to get rid of blower noise/save energy, etc. than folks who
>run 8877 amps. That increases the chance of inrush by many times that
>of tubes that require 3 minutes before keying up. I just think it is good
>financial sense to spring for the $2 for a $600+ insurance policy.
>
>99% of all light bulb failures occur the instant the switch is turned
>on.......
True. I use a 75w reflector flood bulb over my kitchen table. Before I
put an inrush current limiter in series with it, bulbs did not last very
long.
>
>Surely, this economical feature would be included in the parts list for the
>"Nearly Perfect Amplifier" don't you think, Rich?
>
It was not included because heaters don't decrease as much in R when
cold.
cheers, Phil
- Rich..., 805.386.3734, www.vcnet.com/measures.
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