[ARC5] Receiver Power Supply

[Dennis Monticelli]

FYI.  I have a low noise HP precision power supply that is variable from 0
to 100V.  So I did do some experimenting in the past and it agrees with the
general consensus of the thread.  The performance of a stock (only bad caps
replaced and no re-biasing) continuously degrades with reductions in B+.
I noticed minor degradation down to 100V, a pretty significant drop off
below 60V (including BFO start-up issues) and what I would consider an
unacceptable performance dropoff at the 28V filament level.   When running
off a clean bench supply I like to use 90V and when running off 9V
batteries, something like 60 to 70V.   Current draw at 60V is only 10mA
because the leaky caps had been replaced.  Re-biasing would definitely
improve the low B+ situation if one were to do that.  Just rebiasing the
screens would make a notable improvement.

Dennis AE6C



On Wed, Apr 29, 2015 at 2:11 PM, Mike Hanz <aaf-radio-1 at aafradio.org> wrote:

> It seems pretty clear that the "optimum" B+ is a variable, Ken.  Between
> your assessment and Leslie Smith's ~60 volt suggestion, it would seem that
> a variable supply might be a good thing.  For the one or two people on the
> planet who might be interested, I have been fiddling with an idea that
> provides at least a modicum of flexibility, and combines it with a way to
> use your old dynamotor hulks.  It is still a work in progress, but such as
> it is at the moment is at
> http://aafradio.org/garajmahal/virtual_armature.html
>
> Buttoning up the dynamotor end bells reduces the RF noise to about what
> you get with a standard dynamotor, but some adjustment of the original mica
> capacitors on the armature ends should reduce that even further.
>
> 73,
> Mike  KC4TOS
>
> On 4/29/2015 11:40 AM, Kenneth G. Gordon wrote:
>
>> On 28 Apr 2015 at 13:36, D C _Mac_ Macdonald wrote:
>>
>>> I believe some folks here on the ARC-5 list, recommend keeping the B+
>>> voltage
>>> down around 175V or lower to ease stress on the old capacitors in the
>>> receivers.
>>>
>> In my tests on receiver plate voltage, I have found that in several
>> cases, the
>> "best" voltage was "about" 170 VDC or so, although that is most certainly
>> not
>> a "hard and fast" figure either. It seemed to vary a bit between
>> receivers.
>>
>
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