Unfortunately, plain text doesn't convey the tongue-in-cheek and
intended humour of my comment (prompted by not long having received the
info. about the new LDMOS part). Well cared for, tubes will often
outlive their owners; my 60 yr old 813s probably will.
Nevertheless, a single transistor rated at 3-4kW output is an intriguing
prospect and would have been the stuff of science fiction when I started
out in RF design.
Steve G8GSQ
On 09/12/2025 15:34, Steve Bookout, NR4M wrote:
Have you given any thought to converting to some of the Russian tubes.
Would justhave to be an easier rebuild than converting to LDMOSFET’s. And, when I last
looked those tubes are still less expensive than ‘Merican alternatives.
Steve NR4M
Sent from my iPhone
On Dec 9, 2025, at 6:03 AM, Douglas L via Amps <amps@contesting.com> wrote:
I wouldn’t say that using an LDMOSFET is a retrofit.
It would basically mean building an entirely different amplifier with a
different power supply, different input and output networks, etc.
On Dec 9, 2025, at 5:32 AM, Steve Thompson via Amps <amps@contesting.com> wrote:
https://www.ampleon.com/products/extremely-rugged/75-v/ART4K0FX.html
But not the easiest retrofit 🙂
Steve G8GSQ
On 09/12/2025 08:37, Douglas L via Amps wrote:
Has anyone created a work around to replace the 3CX800A7 tubes in the AL-800,
the AL800H, Alpha, Ten-Tec and other amps that used this tube?
Eimac versions are greater than $1500 and the Chinese subs, last I looked, were
pushing toward $1000/tube. Machlett, Penta and the like are simply rebranded
Chinese tubes.
Medical pulls have largely dried up with MRI and other machines going solid
state.
Thus the tube pricing has gotten ridiculous.
Perhaps the only answer is going to solid state amps?
73,
DougWA1TUT
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