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Re: [Amps] AL-80B transformer tap

Subject: Re: [Amps] AL-80B transformer tap
Date: Tue, 24 Jul 2007 10:49:04 EDT
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I have not followed this discussion as closely as others so please excuse  me 
for restating any obvious facts.
When you select the 250vac tap on the Ameritron transformer, you are not  
generating voltages as if the AC line voltage was 250VAC. If the actual line  
voltage is say, 245VAC then the voltages generated are 98 percent of the  
voltages generated by a full 250VAC line.
The killer of tube filaments is over voltage so it seems smart to choose  the 
highest voltage tap that lets the equipment work. A slightly lower than  
"perfect" filament voltage would serve to increase filament life as compared to 
slightly higher filament voltage that would tend to decrease filament  life.
For these reasons, I would also select the 250VAC tap when in doubt.
Gerald K5GW
In a message dated 7/23/2007 7:59:13 P.M. Central Daylight Time, writes:

On Mon,  23 Jul 2007 17:15:52 -0400, James M. Daly wrote:

>So needless to say  I am left wondering what to think. Although my better
>judgment tells me  to at least go the 245VAC route, if not Tom's (W8JI) full
>250VAC  selection, despite what the guy at Ameritron said.

Tom is a very  experienced RF engineer who designs amps. He does a lot of 
science (that  is, controlled experiments and study of the basic principles) 
figure  out what parameters really matter and which don't. Most guys who 
the phone for tech support are bench techs at best, and more likely  minimum 
wage flunkies. Looks like a no-brainer to me. 

Like the man  said -- you got great advice from someone who really knows. 
Follow it and  move on.


Jim Brown  K9YC

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