Try this: http://ad5x.com/images/Articles/Vprotect.pdf 73, Ian N8IK
-----Original Message----- From: Elecraft [mailto:[email protected]] On Behalf Of Mel Farrer via Elecraft Sent: Monday, September 14, 2015 18:31 To: Fred Townsend <[email protected]>; 'Richard Fjeld' <[email protected]>; [email protected] Subject: Re: [Elecraft] K3: reverse 12 volt supply 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 <[email protected]> To: 'Richard Fjeld' <[email protected]>; [email protected] 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:[email protected]] On Behalf Of Richard Fjeld Sent: Monday, September 14, 2015 1:01 AM To: [email protected] 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. >> >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net Please help support this email > list: http://www.qsl.net/donate.html Message delivered to > [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
