[ARC5] running ARC-5 receiever fillaments on AC.

[Leslie Smith]

Hello James/all,
The topic:  What effect is the effect of AC supply to the tube
filaments?

My experience:  First you must understand the power supply I use.

A circuit can be seen on Yahoo - ARC5-radio.  24V AC feeds the filaments
and I rectify/double and regulate to 60V DC.
This is B+.  My problem comes from the fact that I use a common
conductor line for both AC filament supply AND the audio.
When I listen to the audio using an impedance matching transformer to a
speaker - all is well.
When I replace the speaker with low-Z stereo headphones I hear 50 (or
100) Hz hum.

The IR drop cause by 450mA AC in the same circuit as the audio to the
matching transformer (and then 'phones) impresses hum on the signal. 
Why don't I hear it with the speaker?  Oh, I can if I put my ear thru
the speaker cone.  The response of the speaker at 50Hz is much less than
the 'phones.  So I hear it in the 'phones, but not the speaker.

I would use your transformer and use a choke-input filter.
The voltage will be 0.9x the RMS voltage, not 1.41x the RMS voltage. 
105 to 120V.  Not 180V.  
Just  load the PS adequately to avoid the effect of choke-capacitor
resonance in the circuit.


  73 de Les Smith
   vk2bcu at operamail.com

On Sun, Aug 27, 2017, at 07:42, Bill Cromwell wrote:
> Hi,
> 
> I use battery power for both the heaters and the B+. At 90 volts DC on 
> the B+ my radios draw about 15 mA. Your 25 mA B+ supply may be enough. I 
> evolved to pure DC and avoid the AC power supplies because it gets rid 
> of ALL the power line conducted crud. It won't help with atmospheric QRN 
> or radiated junk from a neighbors naughty television but it helps with 
> whats on the power line (because the power line isn't connected to it.
> 
> Somebody else commented about the stability with DC on the heaters. I 
> found the same result. Pipe the audio into your computer sound card and 
> run fldigi, spectran, or other software =with a "waterfall" display. The 
> command receivers will produce a straight line down the waterfall frome 
> stable received signals. That means the oscillators are not wobbling 
> around varying  heater energy when we use regulated DC (or batteries).
> 
> 73,
> 
> Bill  KU8H
> 
> On 08/26/2017 01:03 PM, J Mcvey via ARC5 wrote:
> > Thanks, The reason I ask is that I an old home-brew receiver power
> > supply that someone made.
> >
> > Now the next thing i discovered is that the transformer is probably
> > under -powered.
> > It's a stancor PS-8416 125-0-125 @ 25ma.
> > The rectified voltage may be sufficient but the current is probably too
> > light?
> >
> >
> > On Saturday, August 26, 2017 12:27 PM, David Stinson
> > <arc5 at ix.netcom.com> wrote:
> >
> >
> >
> >
> > From: J Mcvey via ARC5
> > Subject: [ARC5] running ARC-5 receiever fillaments on AC.
> >
> > What is the consensus on ac vs dc filament supplies for the receivers?
> > Does it make a difference? Do they tend to get hum in output?
> >
> > -----------------------
> >
> > It has been my experience that AC filaments inevitably introduce some
> > amount of hum, for various reasons.  YMMV, of course.
> > Dave S.
> >
> >
> >
> >
> >
> >
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