The AM Forum

Hello,
I just Got a Motorola R390/URR.I have been wanting one for some time it works was recapped and retubed in 1988.It is in good shape.Now for a few questions.

1)Why does it have a Radioactive sticker on it?I have heard the meters are the reason but not shure it is the original meters.

2)Where can I get a replacement power cord?

3)The Twin AX plug is a little beat can I just replace with a SO-239 panel mount and be done with it?

and Yes I plan on getting on am I have a Johnson Viking Valiant 2 ready to go I plan on getting on 75 this weekend.thanks and hope to hear ya on am !

Check out this site....tons of 390 info.  Easy modification to use the balanced connector which they claim is more preferred.  Also, if you're going to replace the power cord, be sure to use a grounded one.  Just simply ground the green lead somewhere inside the chassis after it enters from the rear of the receiver.  I think there is information at the below site for that mod also.


www.r390a.com

Ya beat me to it Jay !!

Hi Mike, (love that pix of Jacob on QRZ.com !!)

Radioactive ??? That's the legend !!! Meters.

Here's a direct link for the balanced antenna input. I see no reason why you couldn't use an SO-239 following this proceedure.

 R390A Common Failures  (http://www.r390a.com/Commonfail.htm)

It's a ways down the page!

And any decent power cord should work.

Good Luck.

Buddly'

Gee Buddly, how do you read the 4 point type?  You must be usine the magnifier on your computer.

Mike,
     The meters -- as original equipment -- used radioactive material for luminosity...that's what they meant by "glow in the dark."  Many of the old meters were changed out in depot level repair so maybe yours glow radioactively, maybe they don't.
     I changed the antenna connection and power cord on mine for convenience, but that was almost 20 years ago.  Not as much access to helpful information back then...especially the internet.  For the longest time I bumped along with a "manual" that had more pages missing than present.  Now, you can download everything from the -10 operators manual (less than a meg) to the -40 depot maintenance manual (mega meg)... https://www.logsa.army.mil/pubs.htm  (https://www.logsa.army.mil/pubs.htm)... will help .
     Mine's matched with a Valiant...great AM pair!

It's important to distinguish the R390 from the R390A, and since you're looking for a replacement power cord, the detachable option was only on the R390 so I presume that's the one you've got.

A few things to check for functionality -- the Squelch is very handy for 10 and 15 meters when you're parked on an AM frequency and have the selectivity opened up. It's also handy in the late afternoons down low on 75m as folks gather for AM chats there. The squelch sensitivity is controlled by the RF gain control. Rotating it CCW will normally provide you with a click and a muting function. The BFO can help you center tune and spot the frequency. Sometimes the oscillator is offset, so that the knob on "O" does not equal the frequency tuned.  Unhook the antenna, turn the BFO on, and rotate the pitch back and forth until the rush of the white noise has its lowest pitch. That's the zero point of the BFO, regardless of physical knob location/setting.  Unless you want to go the substitute route because of scarcity, find you some 6082 voltage regulator tubes, a replacement ballast tube, and maybe a couple of 25Z5 rectifier tubes. The rest of the tubes are easy to find.

Shoot us some pictures. Nice radio, you'll have many hours of quality time with it.

Jim, I thought everyone knew that you can increase your web browser's text size by simply hitting CTRL and "+"

Aid to hard-of-seeing.

I'm so good Jim, some say I can see things that aren't even there !!

Yes mine is the older Motorola R-390/URR.I need the plug with the detachable opting that plugs in then has a screw type option.I just need the plug so I can add a three prong cord with the ground.I have many new cords here.thanks Mike