[R-390] New R-390A owner

[Roy Morgan]

At 08:45 PM 6/1/02 -0400, Ronald Davis wrote:
>Hello again
>I want to Thank all for the help with past messages. I was lucky enough to
>find two R-390A's here local. One is in very nice shape and the other needs
>a little work.


You did, of course, buy BOTH of them, didn't you????

>   if it is possible to run a QRP transmitter and use the R-390A
>as a receiver?

Yes, of course.


>  I am wondering if the 5 watts would harm the
>front end of the R-390A?

No, it probably won't

>Also is there a way I can mute the receiver of the
>R-390A while im transmitting.

A terminal strip on the back allows you to mute the receiver and ground the 
antenna input by closing an external contact.  The contact carries 6.3 
volts at about 40 milliamperes AC.  It is labeled "Break-In". The front 
panel switch labeled the same must be on for this to work.


Here are the details I posted recently on this topic.


In short, during normal receive operation, the Break-In switch in the ON 
position  a connection to ground at TB103-9 will shut off both audio 
channels and short the antenna connectors to ground.  (With no connection 
to TB103-9, nothing will happen no matter what you do with the Break-In 
switch.)

Here are the details:

One side of the break-in relay coil is connected to the 6.3 volt filament 
line (AF SubChassis connector P619-10)

The other side of the break-in relay coil is connected to the Break-In 
Switch S-103 terminal 2  through P619-1.  When the Beak-in Switch is in the 
ON position, terminal 2 is connected to terminal 1, which goes to the 
Break-In terminal on the rear terminal strip TB103 -9.

If the Break In switch is in the ON position and terminal TB103-9 is 
grounded (with a wire  to a ground terminal, or through relay contacts on a 
transmitter) the Break-In Relay will be energized.

When the Break-In Relay is energized it does two things:

1) It grounds the AF Line which is the cathode output of the audio cathode 
follower (V601B) and the top end of both the Line Gain and Local Gain 
pots.  This shuts down all audio output from the receiver, both line output 
and local audio.

2) The antenna relay is energized and causes the both the balanced antenna 
and the Unbalanced antenna connector pins to be grounded. This disconnects 
the rf signal input.

Note: If the Function switch is in either the Standby or CAL position, and 
the Break-In Relay is de-energized, the Antenna Relay is energized which 
causes the both the balanced antenna and the Unbalanced antenna connector 
pins to be grounded.




- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan@nist.gov --