Perhaps the -100vdc is used for cutoff bias in receive?
A typical t/r circuit might use a set of relay contacts to lift the + end of
the rheostat from ground on receive thus allowing the full -100vdc to appear
on the center of the rheostat and tube grid(s).
73,
Gerald K5GW
In a message dated 3/22/2008 6:26:27 A.M. Central Daylight Time,
kk7uv@bresnan.net writes:
As a followup to my question about the grid bias supply on the G.E. Ham News
813 amp (and the B&W LPA-1 is nearly the same design):
The bias supplies for these amps use a 120:120 transformer, half-wave diode
rectifier, C/RC filter (40uF/500 ohms/40uF) and a 500-ohm, 25-w rheostat load
for the adjustable bias. These supplies are said to provide zereo to -100v
bias. Yet, the settings for CW and SSB only use -19 volts and -5 volts.
Why then, is it necessary to have -100 volts available? Seems like a much
smaller supply would suffice.
Thanks, Steve KK7UV
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
**************Create a Home Theater Like the Pros. Watch the video on AOL
Home.
(http://home.aol.com/diy/home-improvement-eric-stromer?video=15?ncid=aolhom00030000000001)
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|