The 2N7002 has an internal diode for any inductive collapse. Sent from my iPad Chuck, KE9UW (Jack for BMW motorcycles)
On Mar 12, 2013, at 6:58 PM, "Rich Heineck" <[email protected]> wrote: > Jim, > > The FET shouldn't have had any problem with 50 mA. It's a 2N7002 and is > rated for 115 mA continuous and 800 mA pulsed, with 60V max voltage when off. > One possibility is that the load being switched was inductive (like a > relay), and the FET's voltage rating was exceeded when the relay was released > due to inductive kickback. The simplest solution to snub the kickback spike > is to put a reverse diode, like a 1N4002, across the relay coil (cathode side > to the relay's '+' supply). > > It's also possible the FET was defective or damaged to begin with, which led > to an early failure. > > 73, > Rich AC7MA > > > On 03/12/2013 01:28 PM, [email protected] wrote: >> I blew the switching FET with about 50 ma of current (12 volts) from a >> DownEast Microwave transverter. Elecraft says it should have handled it, but >> anyway, FWIW. >> The FET has been replaced, and an intermediate switching transistor >> installed in the switchbox for the several transverters. Now switching 1 or >> 2 ma, >> hope that holds! >> 73 - Jim K8MR >> ____________________________________ >> From: [email protected] >> To: [email protected] >> Sent: 3/12/2013 12:07:26 P.M. Eastern Daylight Time >> Subj: [Elecraft] KX3 Relay Control For Desktop Amplifiers >> >> >> Most common desktop amps have a relay circuit that requires a transceiver >> to short 12 VDC at 100 ma to key the amplifier on. >> In the KX3 specs, the maximum amp relay current is stated to be 100 ma. >> Has anyone keyed a desktop amp directly with a KX3 or is it recommended to >> use an intermediate external relay circuit? >> >> Thanks, >> >> W9DBR >> >> ______________________________________________________________ >> 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 >> > > ______________________________________________________________ > 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 ______________________________________________________________ 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
