I just received a new AMPEREX 4-1000A today from RF Parts. These tubes are
great and hope to never see a Triton tube again. These are made by a
company in France called Covimag and have massive graphite plates with a
very sturdy mounting that is less susceptible to binding out of axis if
they are dropped in shipping.
Eimac tubes are still good if you can find them but avoid Penta or ETL and
Triton tubes. Also, I have had no trouble with very old RCA 4-1000A tubes
either (all I have were made in the 60's).
I'll test the tube out tonight in my old amp. But my new one is in the
works. It will be some time due to the fact that I lack spare time. But
I'll tell you about it.
1. It will be a vertical design. That is, it will be narrow and tall
and
deep to take up less table space. Power supply in another box not part of
the redesign. I have a pair of commercially built 0 to 8KV .75 Amp power
supplies with electronic current limiting built- in. They have another
feature not useful for ham radio...a dial timer like the ones on the old
microwave ovens but calibrated in hours.
They are painted KY Blue....
2.Cathode drive with ability to apply voltages to both grids to operate
from classical Grounded Grid AB2 to cathode driven AB1. I suspect cathode
AB1 will be most linear.
3. Plate matching network will be a L network with a vacuum capacitor
and
roller inductor. The cap will be from on plate side
and roller inductor will be in series with the output. Being as the
plate
impedance will be greater than 5K and output impedance 50 ohms the Q of
the matching network will be greater than 10. Additional harmonic
filtering will be accomplished by relay selected low pass filters on the
output. Cut off frequencies will be, 2.8, 6, 10, 23 Mhz. No. 30 meter
band. And a 40 Mhz TVI filter always in line.
4. Big window to appreciate the nice red glow of the anode.
5. Tuned Cathode naturally.
6. A delay on the turnoff on the blower. This anode is massive and does
not cool down as quickly an the metal ones.
I would like to see that the plate seal does not get stressed.
May have to back burner the Thunderbolt restoration. Thanks for your ideas
and e-mails about the T'bolt. Does anyone have a slide rule glass and cover
for a thunderbolt they would like to sell or trade??
73
Bill wa4lav
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