[Milsurplus] ARC-5/SCR-274 Receiver HV

[Mark K3MSB]

When using the HP-23 power supply, I run the SCR-274N receivers at 190V via
a dropping resistor.   Never had any problems.

I'm getting ready for another reenactor event and am playing with the BC
and MF receivers, powered by the dynamotors.
Using two tractor batteries in series.   26V is providing 215 V B+.
FYI....

Mark K3MSB

On Sun, Sep 7, 2025 at 1:20 PM <kgordon2006 at frontier.com> wrote:

> On 7 Sep 2025 at 10:23, Ken Kinderman wrote:
>
> >
> > Has anyone had experince with receiver HV lower than the nominal 235 VDC
> dynamotor output? I like to
> > run everything at or slighly below ratings. Not interested in squeezing
> out every last watt from the
> > transmitters, etc.
>
> Yes. As a matter of fact, there was quite a long discussion on this very
> subject on the ARC5
> forum some years ago.
>
> In the case of the ARC-5 receivers, it was found that they worked just
> fine at voltages as low
> as 24 VDC, the only downside of this being that audio output was much
> reduced.
>
> As I brought up at the time, a ham wrote an article on how he reduced the
> operating voltage
> for a Drake receiver in steps to as low as 12 VDC, finding that receiver
> noise was much
> reduced, and the radio worked as well as it did at the higher voltage,
> EXCEPT that audio
> power output was very much reduced. He finally raised the voltage back up
> to about 50 volts
> and left it there.
>
> Our own Dave Stinson routinely operates ARC-5 receivers at 24 VDC.
>
> > So except for the times I am using the dynamotors, I run the receivers
> > in the test jig and out of the racks at about 175VDC, transmitters at
> > about 540VDC. (By the way, even 175VDC is enough to blow the .05's, so
> > I am on a long term quest to replace all, either with re-stuffed cans
> > or just wiring them in. Otherwise, letting them fail is like playing
> > condenser Whack-a-Mole)
>
> And FYI, I found that 170 VDC was about the "best" compromise for the
> ARC-5 receivers
> too, although one had to increase the screen voltage to the same as the
> plate voltage. For
> the ARC-5 receivers, all one has to do is to move ONE wire from the
> junction of the two
> vertically-mounted resistors in the back of the receiver to the hot end.
>
> The RAX series of receivers normally operate at (as I remember it) 180
> VDC. Someone will
> correct me on this, if I am off.
>
> >
> > My question is about the receivers... aside from maybe the 12A6, are
> > there any downsides to lower overall plate voltage?
>
> Screen voltage must be adjusted upwards. Otherwise, there is NO downside,
> other than, as I
> have said, audio power output. And there are certain definite advantages
> to using the lower
> voltage. For one thing, as I said, receiver noise is much reduced.
>
> Ken W7EKB
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20250911/82514061/attachment.html>