Looking a the schematic it appears they use 0V, +V, -V and ACV for the 4 switching states but only + or - voltage is applied to the relays. The big cap is used to smooth out the AC ripple. I would put a back diode across each relay coil and add a MOV of appropriate voltage across C203 (V to ground). Reference the QST article in January 2013 issue. I built one with those guidelines and it's been fine for a couple of years.
73, Brian, K0DTJ ______________________________________________________________ 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]
