[Elecraft] Linear PS Recommendations

[Charlie T, K3ICH]

Boy, talk about LOOOOONNNGG life.  The µ723 regulator IC has been around almost as long as 811-A's !
Wasn't it introduced by Fairchild in the 60's?
I wonder how many ( XX thousands ??) of power supplies have been designed around it.

73, Charlie k3ICH


 

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Myron Schaffer
Sent: Thursday, July 21, 2016 8:42 AM
To: jim at audiosystemsgroup.com
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Linear PS Recommendations

Jim and Clay,

It used to be that way....the RS linear models could not tolerate external voltage present when unpowered, not anymore. Astron has incorporated back-voltage protection through incorporation of some diodes installed in key locations to prevent this.

You can verify if your supply has this modification by looking at the circuit board and see a 1N4001 type diode soldered across 2-pins (can't remember which ones off the top of my head) of the IC voltage regulator LM-723 chip and others hung in various places to protect the pass transistor as well. Usually soldered to the solder side of the circuit board so they are easy to spot. I can't remember is there were some small capacitors added as well.

Any newer (like newer than 1990) linear Astron will have these installed.

Myron WVØH
Printed on Recycled Data

> On Jul 21, 2016, at 12:10 AM, Jim Brown <jim at audiosystemsgroup.com> wrote:
> 
>> On Wed,7/20/2016 10:52 PM, Bob Nielsen wrote:
>> you probably don't need much more than 20 amp capability. I have used an Astron RS-20 for the past 35 years but I would probably go for the RS-35 or RS-50 if I was getting another one.
> 
> That depends on what gear other than the radio that you want to run from it, and whether it is charging a battery which runs the gear or the supply is running the gear directly. It's easy for other 12V gear in a shack to add several amps to the load, and the fancier the shack gets, the more that increases. Clay said he wanted to run all his gear from it (but not the KPA, I am assuming, because it's 120/240V powered). The gear I saw included computer monitors, a K-Line, and some accessories. Perhaps there will someday be antenna relays. And so on.
> 
> Also, the numbers in Astron's model names do NOT correspond to steady state load capacity. It's important to study the data sheets. They are generally well regarded for reliability, but every one I've opened had a bonding problem which is important, but easy to fix.
> 
> Another important characteristic of Astron supplies is that their output regulator circuit is likely to fry if connected to charge a battery but the supply is not powered. Like in a power failure. Ask me how I know this. :) Astron sells a module to place between the supply and the battery to solve this problem.
> 
> 73, Jim K9YC
> 
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