[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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