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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