[ARC5] Army/Navy transmitters from a NON COLLECTOR viewpoint, the ham version...

[Christopher Bowne]

I run ARC-5 transmitters with the SCR-274N  screen modulator.  Besides differences in connector pin outs, and how the B plus is fed to the 1625 final plates, the only difference I noted that mattered when comparing the SCR-274N schematics with those of the ARC-5 was the value of the screen dropping resistor for the 1625s.  I changed the ARC-5s’ screen dropping resistor to match that of the 274Ns’, they sound great when screen modulated with good quality external audio, how good they sound with a carbon mic depends on the condition of the mic.

73 de Chris AJ1G Stonington CT

Sent from my iPhone

> On Feb 9, 2020, at 13:19, J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:
> 
> 
> The FT226 rack will not work with the ARC-5 series (T-XX).
> Get a BC-XXX series to plug into it. it will also accommodate the ARA/ATA units as well.
> They were all screen modulated , except the ARC-5 series.
> More parts would need to be added to the ARA/ATA/SCR-274 series for plate modulation on them, but I suppose the ARC-5 could easily be screen modulated with no modification.
> 
> The regulator on 200V is helpful.
> 
> 
> 
> 
> On Sunday, February 9, 2020, 12:55:49 PM EST, Peter Bertini <radioconnection at gmail.com> wrote:
> 
> 
> I'm probably in the wrong group... but...
> 
> Beyond the bewildering confusion deciphering between ARA/ATA, CBY/CCT, SCR-274, BC-xxx, T-xx/ARC-5 variants... I am looking for a common denominator..
> Assuming one  is NOT interested in the correct accessories, cables, modulators, dynamotors, etc...
> 
> And for the sole purpose of putting any variant on the air with minimal modifications to transmitter itself... don't want
> shelf queens, I want these to be usable and on the air.  
> 
> 1: Can either variant be either screen or plate modulated? I don't see anything that would preclude doing so.. 
> 
> 2: Any suggestions on how a beat-up FT-226-A tray might accommodate either style transmitter? I am thinking having each
> rear connector wired for a particular transmitter pin out, but how to avoid accidentally putting the wrong version in the wrong
> slot? One side Army, one side Navy...
> 
> 3: For power... a modified Heathkit PS-23 junker... get rid of the voltage doubler nonsense and use full wave bridges on the
> high and low voltage windings. Series the two to provide around 125 vdc for the RX, and around 500 vdc for the TX.
> 
> 4: Add a half-wave voltage doubler on the 12.6 winding for DC filament voltage for the transmitter filaments and relays.
> 
> 5 Any benefit to regulating the 200 VDC for the 1626 oscillator? I suspect it would not hurt. 
> 
> 6: transmitters will be modified following AB5S's suggestions regarding relay adjustments, etc  
> 
> Flame away...
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