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

[David Gow]

One common suggestion is to run them first on  the lower voltage CW setting
but leave the key down long enough  to get the anodized nice and red.  Do
this for several times and then use them normally in SSB in the CW setting
with enough talking, slow cw or carrier to get them red in normal operation
.  Eimac says showing color is fine and normal, not bright orange.    After
some use switch to SSB setting and then you will get your 1200 watts with
about 2400 volts on the anodes, 90 watts drive and 220 mils grid current.
Very old Eimac tubes go into service more re,liability than mid range tubes
as Eimac had significant 3-500z problems when they moved to the Salt Lake
City plant, at least that is the story most heard.
Dave W7VM

On Fri, Dec 23, 2022 at 1:47 PM Joe Subich, W4TV <lists at subich.com> wrote:

>
>
> > Of course, the finals in the Amp are push pull configuration -2k PEP
> > & 1K CW input watts.
> That is incorrect.  The L4B (and L7) are parallel 3-500Z designs.
>
> If your "new" tubes come from Drake, they are quite old - even though
> unopened.  I'd put them both in and bring them up slowly but be prepared
> to bite the bullet for brand new tubes if necessary.
>
> 73,
>
>     ... Joe, W4TV
>
> On 2022-12-23 3:48 PM, A Lawrence Fibich 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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