Very true Roger.
That is a real problem and it makes it hard to make sure you don't go
too far the other way. I do my calcs when the line votage is high and
set the filament volts 2-3% higher than nominal. That gives me some
confidence that it will still be ok when the line voltage drops at
the high usage times of day.
73, Alek.
At 09:52 AM 29/01/2010, Roger wrote:
>Alek Petkovic wrote:
>>G'day Rob
>>
>>It is not any "camp" that makes the claim of shortened emissive
>>life due to high filament voltage. It is Eimac, in its "Care And
>>Feeding" book. For every 3% increased in filament voltage, the life
>>is shortened by 50%. In the case of Ameritron's 10%, one would
>>expect around 12% of normal tube life. (Didn't someone recommend
>>Ameritron here a couple of days ago on a different thread? Ha ha)
>>
>Don't forget, that line voltages can vary over quite a wide range
>and there are taps on many transformers to adjust for the proper
>output voltage. Line voltage can easily vary up to around 10%. I
>don't know what the specs are now for AC, but it "used to be pretty
>tight". Still I remember a couple of times back in the 60's and
>70's of calling the power company because we were going through
>light bulbs like crazy. We were at the head end of a very long line
>so we ran near the upper limit just to get enough voltage to the other end.
>
>Current line voltage right now is 118/236. I've never seen it go
>outside 115-118 except for some failures.
>
>73
>
>Roger (K8RI)
http://www.qrz.com/db/vk6apk
http://www.qrz.com/db/vk6py
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|