[ARC5] T-19 Update

[Christopher Bowne]

IIRC, the modulator BC456 and MD7 modulator power units only actually key the MO 
plate and final screen voltages to transmit on CW and MC ,with the 1625 plates 
having HV on them  whenever the dyno is running, which is continuously in CW and 
MCW.  Of course in voice mode, the dyno itself is keyed to start on transmit.  
What some think is a "keying" relay in the final cathode circuit is actually the 
TX "select" relay which, in a multi transmitter setup, returns the cathodes to 
ground of the set that is selected by the transmitter select switch on the TX 
control box, the same circuit also  locks  on the transmitter's antenna connect 
relay to connect the tank circuit to the antenna post.  Neither of these relays 
on the transmitter chassis otherwise follows keying in the original design.  The 
external antenna relay that shifts the antenna from the transmitter to the 
receivers does follow keying of course.

This is based on my memory from when I set up my "hybrid" ARC-5/274N system of 
T19/T22 transmitters, BC-456 modulator, and ATA antenna relay (one of those with 
the build date clipped off the nameplate), and BC-450 transmitter control box.

Chris, AJ1G
Stonington, CT


________________________________
Frh, inom: David Stinson <arc5 at ix.netcom.com>
To: ARC-5 List <arc5 at mailman.qth.net>
Sent: Thu, December 20, 2012 8:17:59 AM
Subject: Re: [ARC5] T-19 Update

Fellow ARC-ites:

Can a couple of you please take a few minutes to look at the ARC-5 and 274N 
modulator power distribution
diagram and see if I got these right?  I've checked repeatedly, but I'm just a 
human... I can make mistakes.
If everything is "right," his rig should be working.
If I ever actually built these dividers, I don't remember it.
I run my rigs with the original modulator and racks.

http://home.netcom.com/~arc5/ARC5/ARC5PWR.jpg

http://home.netcom.com/~arc5/ARC5/274NPWR.jpg



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