Date: Fri, 23 Dec 2022 20:48:28 +0000 (UTC)
From: A Lawrence Fibich <lfibich@sbcglobal.net>
To: "amps@contesting.com" <amps@contesting.com>
Subject: [Amps] Requesting opinions on a Drake L-4b's tubes
<I just acquired this Drake L-4b as the third owner and no nothing about
its history. It puts out <400 watts with recommended Plate and grid
currents (.56 amps, and 225Ma respectively). If <overdriven (.8 amps;
100ma) it will do 600 watts. At 'idle/resting' should be 0's but shows .1
<plate amps & 75 ma grid current- which I think shows a tube problem.
<Now my request for an opinion, what do you suggest:??
<1. I got 2 unopened tube boxes from Drake - thinking to simply replace/use
them and see <what happens.
<2. Surprise - 1 is the 3-500G- (Graphite plate) - the other turns out to
be a 3-500Z (old style) <3. The unit has 2 (original/old) - 3-500Z's in it
and really no way to test them4.? So? what to <do?5. Live with it, and
leave the 2 in the unit and live with 400 watts and? or- maybe <overdrive
them and go for 600 watts? ? how long do you think they would last?6. Use
the '<new' 3-500Z with one of the 'old' 3-500Z's?7. Use the 'new' 3-500G
(graphite) with the 'new' <3-500Z?8. Use the 'new' 3-500Z with one of the
'original/old' 3-500Z??
<Of course, the finals in the Amp are push pull configuration -2k PEP & 1K
CW input watts.?
<Thanks for ALL your suggestions/recommendations.??73Larry F.W6EF
## I own four drake L4B's. use a PEP meter to tune it up, and with 60
wpms dots.
On 75m, I get 1290 watt pep out. Then hit it with a brief 2 second cxr to
get steady state plate and grid current readings. Should be 800 ma plate
current..and 300 ma grid current.
## apply just a bit of drive initially, like 10-25 watts (60 wpm dots) and
tweak the tune control for max output, then the load control. Then apply
more drive and keep repeating the process.... until 1200-1300 w pep occurs.
Jim VE7RF
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