[ARC5] R-27/ARC-5 Hookup Question

[Kenneth G. Gordon]

On 19 Jul 2013 at 18:21, J. Forster wrote:

> Ken,
> 
> Connected normally, the final audio stage B+ does not go through the
> choke.

True.

> If it's biased Class A, the final stage could draw more than
> the rest of the set. If it idles at 50 mA, the transformer will
> dissipate 1W roughly.
> 
> It's not obvious what the parts of the receiver draw for B+.

I have measured the total current draw of my radios when the audio gain is 
cranked up all the way with a modulated RF signal input to the radio: it was 
about 50 mA.

The dynamotors are rated at 60 mA output.

At 50 mA through the choke, the voltage drop would be about 15 volts (using 
an average internal resistance of 300 ohms), or 0.75 watts.

As I said, Fair Radio Sales units fed all the voltages through that rear-panel 
connector, and their units were quite popular.

There is one minor thing that "bothers" me about feeding the +HV to the 
radio through that rear-panel connector and that is that if the +HV come from 
the dynamotor, the plate voltage to the 12A6 is a bit higher than it is the rest 
of the receiver, as was common with most radios of the time. Feeding the 
+HV through the rear-panel connector reverses this relationship.

It may not matter, but it IS different.

As far as the choke is concerned, I have no worries connected with it at all.

In fact, I have used that choke in several AC supplies and it works very well.

Ken W7EKB