[Elecraft] Linear PS Recommendations

[Richard Fjeld]

I was glad that I caught Jim's remark about blowing the 723 by being 
connected to a battery with the PS off.  And also Myron's answer.

Back in the tube TV days, I purchased a bare circuit board at Radio 
Shack, (I think). The board was similar to an Astron circuit board, but 
simpler.  I rewound a heavy transformer from a color TV and made my 
first 13.8 Volt power supply to use for a Heathkit HW-104.  Years later, 
the 723 went bad.  It may have been due to the stated reason, I can't 
remember now.  I did some repair work on it and still have it.

Someone on the reflector provided the following link one time, which I 
think is a good idea for an extra measure of over-voltage protection or 
accidental reversal in polarity. I remember discussion about a reversal 
that happened to someone on the reflector not long ago.

I hope the link still works on here.  If it doesn't, it is on ad5x dot 
com website. Look for a Vprotect pdf file.
http://ad5x.com/images/Articles/Vprotect.pdf

Dick, n0ce


> On 7/21/2016 7:41 AM, Myron Schaffer wrote:
>> 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

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