Jason Buchanan <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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john wrote:
john <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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What kind of grid current to you L7 users see, when the amp is fully
loaded on CW?
I don't know about other guys but I never look at grid current -
occasionally I'll flip the meter to view it when I get tired of watching
plate voltage but I don't like banging the needle around. You should
tune for max output and never increase output beyond the point where you
get a linear rise in output to exciter input. Grid current rises
rapidly when you are overdriving things. I use the relative output
position on my L4 when tuning up - over time i've learned how much drive
is required for CW or SSB position - about 50 watts is the safety zone
for CW position and around 80 for SSB using 3-400Z tubes.
Tune for maximum output at around 800 watts, increase drive until you
reach max smoke without adding more LOAD to reduce grid current (you may
have to touch up the plate or load a little but don't increase load to
reduce grid current for this test). Then back off drive so that your
output from the amp is reduced about 200 watts and you'll most likely be
running with no more than 250mA grid current.
For me, a pair of 3-400Z produce 1200W when run to ridiculous levels but
at 1000W they are way more comfortable in terms of grid current and
plate current. The stock L4 fan can't keep the tubes cool for sustained
1000W output runing CW in the high voltage SSB position so I usually run
the amp in CW mode for about 600 watts output - the tubes will last
another 40 years that way. I never exceed 200mA grid current in either
mode when I run 600W output in CW position, or when I back off 200W from
max smoke in SSB position.
This is more info than you wanted but I thought i'd throw it in hi
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73 Jason N1SU
Jason Buchanan - Boxboro, MA
Website: http://n1su.com/
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