[ARC5] Receiver current drain

[J. Forster]

OK. If the supply naturally drops below the Zener string, the voltages are
fine. IMO, the Zener clamp is the easiest way to go, as I originally said.

Best,

-John

=================


> On 6 Jan 2011 at 6:22, J. Forster wrote:
>
>> Hi Ken,
>>
>> I'd be inclined to go a few volts higher on the diode string, so the
>> Zeners are not turned on when the radio is operating.
>
> Hello, John:
>
> In these particular power supplies, there is enough series resistance in
> the
> filter system after the transformer that with any load beyond the Zener
> load,
> the output voltage will be lower than 250 VDC.
>
> For instance, with a load of 23 mA, the output voltage is 242 VDC.
>
> Therefore, I figured that the only thing I needed the Zeners for is to
> clamp
> the unloaded 350 VDC to 250 VDC until the receiver load picks up, when
> they will "drop out".
>
> I figured that doing it this way will almost perfectly emulate the
> original
> dynamotor power supply which outputs 250 VDC as soon as it comes up to
> speed and before the tube filaments warm up.
>
> At 40 mA load, the output voltage of these power supplies is on the order
> of
> 165 VDC.
>
> I suppose I could adjust the series resistances (there are three of them)
> so
> that the Zeners would provide regulated 250 VDC output, but I am trying to
> keep this as simple as possible.
>
> The transformers are capable of about 70 mA at least.
>
> In my past experimentation with B+ voltage on ARC-5 receivers, the optimum
> seemed to be 180 VDC, so these power supplies will be just fine.
>
> Thanks for the input. I very much appreciate the information I get here.
>
> Ken W7EKB
>
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