[ARC5] 10 meter BC-454 - screen voltage

[Dennis Monticelli]

My own experience has caused me to settle on about 60 to 70V.  The
sensitivity is enough for DX and the audio is sufficient to put 50mW into a
speaker. I noticed that BFO start-up was an issue on 24V for one set I had.
Perhaps that was an anomaly.  I have not experimented with the screen
divider but I can see where that could be fruitful.   If the caps are in
good shape (or replaced), the B+ current is only 10mA at 60V so a stack of
9V batteries will operate the set in the field (lead-acid for the
filaments).

Dennis AE6C

On Sat, Mar 9, 2013 at 2:36 AM, David Stinson <arc5 at ix.netcom.com> wrote:

>
> ----- Original Message ----- From: "john rose" <brokenthumb at live.com>
>
> Subject: Re: [ARC5] 10 meter BC-454 - screen voltage
>
>
>  ...It is designed to run on 24 volt B+ and is loaded with tubes designed
>> to run at this level (26A6, 26C6, 26D6 etc)....
>> Will the tube really run at that B+? ....
>>
>
> I routinely test Command Set receivers in completely "stock" condition and
> run them for hours on 24 VDC B+.  Sensitivity is a little down and audio is
> headphone level
> ( I use an amplified external computer speaker - cheap as dirt at yard
> sales ).
> I'm not trying to work DX with a Command Set receiver,
> so a minor reduction in sensitivity is no issue.  In fact,
> they run cool, stabilize faster and the noise floor is better.
> I've run some for years this way and never encountered
> a "downside" I considered significant.
>
> Many of us run them a varying amounts of reduced B+.
> Some make changes to the screen voltage divider
> but I've never had a need to do this.
> I have found a "breakpoint," however:  Something changes between about 75
> and 110 VDC.
> I tried 90 VDC and the receivers just sound "crummy."
> Audio is distorted.  Down at 24-28 volts and above about 150, they sound
> fine again.
> One of you Smart People should tell us what's going on.
>
> In fact, I've run an entire stock SCR-274N on straight 28 VDC for fils and
> B+.
> It was QRP TX power and headphone audio,
> but it worked spendidly.   Got to hand it to those A.R.C. engineers.
>
> 73 DE Dave AB5S
>
>
>
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