>
>Hi folks,
>
>I finished restoring a two-hole 76A a few months ago, and
>it seems to be running fine. (nice little amp) My question:
>
>With the original attenuator, (resistor pack) I get roughly
>650-700 watts out for 75 watts drive. I don't really want to
>run it much harder than that, but does 75/650-700 with the
>stock pack sound about right? I would guess so, but never
>having played with an amp so heavily "swamped" on the input
>before, it's hard to know for sure.
>
- If I owned one, I would put an ultrafast recovery diode in series with
swamper-R. The diode's arrow needs to point toward gnd in order to
provide loading on the positive half of the driving cycle - where the
cathode draws virtually no current. This config. removes the swamper
from the burden on the exciter during the negative half of the driving
cycle. / Mouser carries such diodes. /
- A useful mod on older Alphas is to replace the orig., 350v-max,
unstable, carbon-comp, "equalizer" resistors across the 450V electrolytic
capacitors with modern MOF resistors. If these capacitors have a date
code prior to 1980, they should probably be replaced.
- For SSB service, 8874s are best tuned up with a tuning pulser to avoid
stripping the oxide coating off of the cathode. [photo on p.17 in Sept.,
1990 QST article, "Parasitics Revisited"]
cheers, Jim
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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