[Elecraft] OT: Repairing Astron RS-20

[G. Beat]

Harold,

A couple of suggestions in repairing your Astron.  
You MUST discharge the large filter capacitor before removing or replacing the LM723 regulator IC (this is the part you will likely have to replace).

The RS-20 uses 2N3055 pass transistors, but you can also use 2N3771 (which is what Astron has been using on newer units).  Test the pass transistors, IF you are replacing the LM723 (testing with a VOM is covered in the KBT web site - below)

Excellent reference web site for understanding, troubleshooting and repairing linear power supplies
http://www.kbt-dc-supplies.com/index.php

Dave Metz, WA0AUQ's  article "What Inside Your Astron?"
http://www.seits.org/features/pwrsup.htm

This is a very easy repair, and it one of the Amateur technical basics (audio, power, antennas) that I teach new amateurs.

Astron schematic diagrams
http://www.repeater-builder.com/rbtip/astron-index.html

Greg
w9gb

> Message: 11
> Date: Mon, 13 Dec 2004 09:47:45 -0600
> From: "James" N5TOG
> Subject: [Elecraft] OT: Astron RS 20 schematic
> 
> Would some one have a schematic for an Astron RS 20 power supply they could 
> email me or know were i can find it.
> Sincerely Harold N5TOG  K2 1587