[Amps] Requesting opinions on a Drake L-4b's tubes

[Jim W7RY]

Better yet...

How much drive are you putting into it?

What radio are you using?

Jim W7RY


On 12/23/2022 6:36 PM, Curt Nixon wrote:
> 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 at 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 at 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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-- 
Thanks and 73, Jim W7RY