Don - Thanks - that 's exactly what I needed to know. I've measured an open circuit voltage of 16.2VDC at the amp keying RCA jack and current of 116mA when the relay is closed. These parameters are well below the limits of the K3 keying circuit, so I'll remove the buffer interface unit.
I see from the AL-811 schematic that there is a 1N4007 across the relay, which is there to block any back EMF pulses from being applied to the keying line, I guess. That was my other concern, whether these transients would damage the K3, but I guess the amp designer put the diode there for that. I'm only using this amp for SSB phone, so QSK is not needed. My amp is nearly 25 years old ( 3 owners now) - it has the original open frame relay: slow and noisy, but still reliable. What I'd REALLY love, of course, is a KPA 500 :) But this old AL811 is humming away perfectly on a set of 572b tubes and I don't have the heart to get rid of it until something expensive goes wrong. I'm off to rationalise my shack wiring - one less black box! 73, John VK7JB ______________________________________________________________ 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
