[AMRadio] R-390A Help


Bill Guyger via AMRadio amradio at mailman.qth.net
Tue Jul 8 14:49:18 EDT 2014


Interestingly, the very first thing I remember building was a Neon Relaxation Code Practice Oscillator in the mid to late 50's, I must have been 8 or so at the time. It had a Selenium rectifier that fried and I remember the stench to this day. My mother was not too impressed either. 

Collins and then Continental used them as snubbers across things like the Plate Choke in broadcast transmitters for a pretty good while (I don't think they still use them) and the drill is to get them the heck out of circuit. They were for surge suppression so they basically didn't do that much and if they did go.............wow!

When the Mexican singer Selena was murdered a number of years ago, all the Hispanics in the area were driving around with "In Memory of Selena" painted on their rear windows. I mounted an old rectifier on a piece of poster board that said "In Memory of Selenium" on it and stick it in the rear window of my car. Nobody ever smashed my window and my engineering buddies got a snicker so guess all's well that ended well.

Bill 


On Tuesday, July 8, 2014 1:01 PM, "djed1 at aol.com" <djed1 at aol.com> wrote:
  


Ireplaced my ballast tube with a resistor 30 years ago (the internet hadn't been invented yet, and it was hard to find a spare 3TF7).  I've had no regrets, and a 40-50 ohm resistor is the simplest solution to the ballast problem.
The solid state replacement for the rectifiers is a well-documented Navy fix.
I'd bet on the filter caps being a problem, but the troubleshooting technique recommended sounds fine.
 
 
 
 
-----Original Message-----
From: W2xj <w2xj at w2xj.net>
To: Bill Guyger <bguyger at yahoo.com>
Cc: Discussion of AM Radio in the Amateur Service <amradio at mailman.qth.net>
Sent: Tue, Jul 8, 2014 12:45 pm
Subject: Re: [AMRadio] R-390A Help


You should really download an on line version as some have more detail and 
background information.  I should note that every single tube in that radio can still be bought as old 
stock never used online.  These guys have everything but the ballast tube which can be had from fair radio http://www.vacuumtubes.net/prices.htm Rectifiers are $20 each and the ballast is $60 while the other tubes are between 
$3&$7. That is a good reason to go solid state on those three expensive tubes.  Sent from my iPhone > On Jul 8, 2014, at 11:51 AM, Bill Guyger via AMRadio <amradio at mailman.qth.net> 
wrote:
> 
> Thanks to all that replied, now to go diggin'! Just wanted to see if any of 
you had any hot sports opinions before I go hunting.  Shouldn't be a real chore 
once I get time, a manual was included along with the radio.
> 
> Tnx 73 Bill AD5OL
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