> Hello all,
>I have a couple of questions regarding the Henry 3k Classic X MKII
>amplifier. As most of you are aware, this amplifier uses a single 3CX1200A7
>tube in the RF deck. My question is, How difficult is it to convert this amp
>into the 5k dual tube version?
One 3cx1200A7 has 0.8pf of feedback C Two of 'em have 1.6pF of feedback
C. Are you trying to build an oscillator?
- the 3cx1200Z7 has 0.08pF of feedback C. It is a poor choice for
building an oscillator.
>Does anyone know if the stock filament
>transformer is up to lighting both tubes? Filament requirements are 7.5
>volts at 21 amps per tube, so this is quite a bit of current to light the
>tubes. I know the B+ supply is certainly up to the task, this beast has an
>enormous power supply easily capable of supporting 2 tubes. Other than the
>obvious things such as mounting the extra socket, wiring up the tubes in
>parallel and connecting the extra anode lead and parasitic suppresor, is
>there any other mods required to make this conversion? I of course would
>fully expect to have to adjust the idle current, and retune the input coils
>due to the extra tube. I also learned of others having trouble with the
>factory filament choke in the 5k versions of this amp. Something on the
>order of the choke being wound improperly right from the factory, and
>causing a hum in transmit. The amp presently has no hum issue with a single
>tube, but can I expect this if I add another? Henry of course doesnt care to
>be bothered with any questions unless your waving hundred dollar bills in
>their faces, so thats the reason for this post. Any light that can be shed
>on this would be much appreciated.
>
>
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>
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
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