[ARC5] Dynamotor Questions

[Rich Post]

Hi Wayne,
I assume you are trying to run a BC-348 with its original dynamotor.  For
power, you can run the filaments at AC from one source and the dyno on DC
from another.  The DC supply would only require about 2 amps.  It wouldn't
take much to cobble up 24 VDC at 2 amps with a decent end electrolytic to
assist the starting surge. Unfortunately I have never had that opportunity
with a BC-348 since my 348's and 224 were all converted before I got them.
However, I did run several Command receivers using one of those Knight or
Eico battery eliminators that were used as car radio substitute power
sources back in the day.  Those go for relatively cheap at hamfests.  At
low current with silicon rectifiers, the voltage can get a lot higher than
12 VDC.

One of the 3 Command receiver dymos I tested was a Continental Electric
that was size and plug compatible but had original gray paint. Here are my
notes from an article written several years ago.
---------
"While the same size as the other two, it was capable of up to 85 mA at 250
volts and may have been intended for a later VHF Command set, many of which
also came with gray paint.  I not only lubed it, but had to take it apart
to repair the flaking rubber-covered wires to the base plate connector.
Afterwards I tested it.  It ran beautifully at 24 volts input and 250 volts
at 60 mA output to my two-series connected (7 watt) night lights.   I could
not test it at 28 volts input, because my Knight battery eliminator power
supply topped out at 24.6 volts given the greater current draw at 1.7 amps
instead of 1.1 of this more powerful dyno.  At just 5 volts input, the dyno
was still pumping out 41 volts at 20 mA.
To no surprise, the 3 dynamotors easily powered the Command receivers."
------
You can run filaments on about anything, but if you use half wave DC
(direct diode off AC with no filter caps) the filaments will see an
equivalent heating DC power of 0.707 times the input AC.

Best wishes experimenting es 73,
Rich KB8TAD










On Mon, Dec 18, 2023 at 5:48 PM <releazer at earthlink.net> wrote:

> The idea to use half wave DC was just to avoid having to come up with a
> regulator.  I have a couple of 28VDC power supplies I built to run my
> ARC-114 and ARC-116 but they may be a bit low on current capability.  And
> my HP variable DC bench power supply has suddenly decided that it will not
> produce the full rated 200W 0-150 VDC output but rather more like 1.5 amp
> DC max.
>
> By the way, I rewired a 21 VDC (not a typo, 21 VDC) dynamotor with the two
> primary wirings in parallel rather than series to see if it would provide
> half the output voltage on 12 VDC.  It worked to a limited degree, but only
> slightly better than just running it on 12 VDC without the rewiring.
>
> Wayne
> WB5WSV
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