[Milsurplus] RBC Power Issues
David Stinson
arc5 at ix.netcom.com
Sat Sep 30 12:00:17 EDT 2017
Meant to include this:
Don't have an RBC power supply and the receiver power
connector is missing in any event.
The RBC is speced for 200 VDC general B+, 105 VDC Regulated for
the Local Oscillator, 6.3 VAC general filaments and
17 VAC, which is "regulated" through a Ballast Tube and
resistor circuit to provide 6 V to the LO tube.
Don't have that filament ballist tube. Have had no trouble
just running the regular 6 V fil. buss to the LO, which was
done by the previous person working on the set. I'm thinking
of rectifying and regulating the fil buss to the LO, but doesn't
seem necessary so far.
The 105 V B+ buss for the LO draws only 8 mills, so I
installed a 12.5 KOhm 5 Watt resistor and a 100V, 5W Zener
to power that buss. Works fine.
200V B+ buss is easy to regulate these days with a MOSFET
and that will "leaven the whole lump." Total current draw
for the B+ buss is about 75 mills at full volume.
For those who prefer "Low B+," the set operates reliably
at 100V B+ on both busses. Loses about 6 DB of Audio Output
at 100V and a small but noticeable reduction in audio quality.
The BFO oscillator doesn't start reliably below about 75 VDC,
but the set will play AM down 50 V. with, of course,
a reduction in audio output and quality.
Still chasing a few little "gremlins," but things are looking good.
Dave S.
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