[ARC5] T-19 Update

[Mike Everette]

Chris, you are quite correct in your analysis.

I've been following this thread but have not jumped in until now... it really surprises me that there could be so much trouble with an ARC-5 transmitter.  Could it be something as simple as the connection between the little coil spring contact which the "antenna" relay moves to select the transmitter, not making to the antenna post?  Hmm.

If the little spring is missing, is there any sort of connection between the antenna post and the "arm" which comes up from the loading coil, where the spring would normally be?

Or, try this.  You might be surprised to find out that the antenna loading coil has become so oxidized that there is no connection between the wire and the roller contact!  Yes, it COULD be, indeed.  Seen it before.

Use some contact cleaner and a paper towel; scrub the winding of the coil, then clean the roller and the brass shaft that it runs on.  You do not have to disassemble anything or remove it from the transmitter.

DO NOT start turning the two screws with blue heads, which are the slugs in the VFO coil and the PA tank coil.  You will really regret doing that.

73

Mike
W4DSE


--- On Thu, 12/20/12, Christopher Bowne <aj1g at sbcglobal.net> wrote:

> From: Christopher Bowne <aj1g at sbcglobal.net>
> Subject: Re: [ARC5] T-19 Update
> To: "David Stinson" <arc5 at ix.netcom.com>, "ARC-5 List" <arc5 at mailman.qth.net>
> Date: Thursday, December 20, 2012, 6:53 PM
> 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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