Seems odd that you say overdrive giving 100ma of grid but 400w with 225ma
grid..
This is perhaps a tuning issue with mis adjusted loading. Are you using
relative output and grid current to tune or trying to dip the plate
current. What is the plate hv doing in those two conditions?
On Fri, Dec 23, 2022, 6:31 PM A Lawrence Fibich <lfibich@sbcglobal.net>
wrote:
> Please accept apologies - I misspoke on being push pull - surely finals
> are in parallel - I was more focused on trying to explain simply and
> 'fingers did their thing' again, sorry for misspeaking. LarryW6EF
> On Friday, December 23, 2022 at 12:48:28 PM PST, A Lawrence Fibich <
> lfibich@sbcglobal.net> wrote:
>
> 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
>
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