>
>The sb230 has one 8873 tube.
>The manual says power input is 1200 ssb 1000 cw 400 rtty
>
>Yes, and the one I have works very well. The only downfall I would
>mention is the extra "loud" TR relay.
The stock relay is also too slow for modern radios. A suitable high
speed switching circuit is shown in "The Nearly Perfect Amplifier" in the
1/94 QST.
...snip,,,
>I've heard mention that the SB-230 has some parasitic problems when used
>on 20 or 15 meters, but I've never had any problems so far with my
>limited use there.
Typically, a shorted1000pF feedthrough capacitor in the grid circuit is
indicative of such an occurence. The capacitor shorts when an anode to
grid arc occurs as a result of gold-sputtering from the grid during the
parasitic.
The 230 uses no vhf suppressor in the vhf-resonant anode circuit, even
though the hv-rfc is isolated from the anode circuit with a vhf
attenuator bead. Some owners have reportedly been able to improve the
vhf stability of the 230 by slipping a pair of type-73 vhf attenuator
beads over the anode lead.
Note: a gold-sputtered 8873 can often be made usuable by moving the loose
gold melt-balls into the base. Interested parties are invited to contact
me.
...snip...
Rich---
R. L. Measures, 805-386-3734, AG6K
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