.......
>I am rebuilding a sixties-era homebrew amp running a pair of 4-400s in GG.
>The power supply is a full-wave, capacitive input circuit. Recently I
>discovered that the high-low voltage switch on the power supply actually
>switched between two primary taps labeled 5,000 volts and 2,500 volts,
>respectively, for the secondary. I have not yet tested the PS for actual
>DC output.
>
>The output circuit is a standard Pi tank with fixed inductor taps on B&W
>coil stock. The values of C (tune) and C (load) and the inductance are
>unknown.
>The question: changing the Ep by fifty percent (50%) while keeping most of
>the other variables constant will vary the Q and should require retuning.
There will be not much difference if the current is changed
proportionately, Ron. 5kV at 800mA yields about the same RL as 2.5kV at
400mA---and a difference of 1 S-unit at the receiving end.
- Although 5kV is above the key-down A-zero/N-zero-N rating, 4-400s with
good vacuums have reportedly been successfully operated at such voltages
on SSB. This is not surprising to me since the published AM rating of
3200v is actually 6400v under 100% modulation.
- If I were designing a SSB amplifier with 4-400s using a 5kV anode
supply, I would copy the SB-220's cooling system, use a ZSAC of 70mA per
anode, use a tuning pulser for tuneup, and use the lowest VHF-Rp
parasitic suppressors I could come up with. ....... More volts produces
more HF amplification AND more VHF amplification.
Rich---
R. L. Measures, 805-386-3734, AG6K
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