Hi Matt,
Unfortunately the D7 and A7 are not directly interchangeable as the filament
voltage is different.
3CX1200A7 7.5 V at 21 A
3CX1200D7 6.3 V at 25 A
The D7 was indeed developed to be a better performing tube above HF but
turned out to be not the improvement Eimac hoped for.
However, it is a shorter tube and has larger anode fin area. The shorter D7
is used in the 3KD desktop for that reason.
At HF as you can see both work well in HENRY amps.
Carl & Rich state that for homebrewers the A7 may require paying attention
to stability issuees on 10M.
73, Dan Magro W7RF, (member SCDXC, SCCC)
Rugged, Reliable Henry HF Amps are "Instant on" for RF Power now!
DXers/Contesters/Ragchewers get your HENRY from RADIODAN for LESS!
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> -----Original Message-----
> From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
> Behalf Of Matt--K7BG
> Sent: Thursday, October 08, 1998 7:30 AM
> To: Bob Marston; amps@contesting.com
> Subject: RE: [AMPS] What Tube for Home brew
>
>
>
> > The changes in the D7 did not address this problem to any
> >appreciable extent.
>
>
> Ignoring the latest and greatest "Z7" for the moment. What exactly are the
> differences between the A7 and the D7? I searched all the amp archives and
> found nada. Are the 1200A7 and the 1200D7 interchangeable?
>
> 73, Matt--K7BG
>
>
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