[Elecraft] K3: reverse 12 volt supply

[Mel Farrer via Elecraft]

You guys are working too hard on this.  Here goes:
Take a bridge rectifier, preferably a Schottky with proper current and voltage rating.  Tie the + to the radio + tie the - to the radio -.  And I don't care what polarity you put on the AC terminals it always give the radio the proper polarity,  I put a little box on the back of every portable radio when we go camping etc.  That is after my brother reversed the polarity on my TS-50 and we let the smoke out.
Mel, K6KBE

      From: Fred Townsend <fptownsend at earthlink.net>
 To: 'Richard Fjeld' <rpfjeld at outlook.com>; elecraft at mailman.qth.net 
 Sent: Monday, September 14, 2015 3:13 PM
 Subject: Re: [Elecraft] K3: reverse 12 volt supply
   
Dick:
Relays? Sure, easy to do. Power relays are often used in many kinds
equipment. They are sometimes called 'contactors'. They are either big and
clunky or small and unreliable. Which kind do you want and what are you
willing to pay?
73
Fred, AE6QL


-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of
Richard Fjeld
Sent: Monday, September 14, 2015 1:01 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3: reverse 12 volt supply

I would think you could wire a relay with a diode in the path to the coil so
that it would not operate if the polarity of the power leads are reversed.
That way, there would be negligible voltage drop when operated.

Dick,n0ce


On 9/13/2015 10:09 PM, Don Wilhelm wrote:
> The base K3 is protected by an in-line diode that will not allow 
> reverse voltage to flow.
> The same is not true of the KPA3 where the reduction in voltage would 
> not be tolerable.
> The KPA3 is protected by a circuit breaker, but in this case did not 
> trip in time to prevent damage.
>
> 73,
> Don W3FPR
>
> On 9/13/2015 10:55 PM, James F. Boehner MD via Elecraft wrote:
>> Whew!
>>
>> Not a good feeling-but it can happen to any of us, regardless of how 
>> careful we are.
>>
>> Elecraft has been very good on suggesting helpful modifications to 
>> the radio.  Any thoughts? Perhaps an in-line diode?
>>
>> I'm not sure if that would result in a significant voltage drop-just 
>> a thought.
>>
>>
>
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