No replies to this one yet, but I have spent a bit of time looking over the schematic and poking around with my DMM & scope. Here's what I've found so far:
TX (RD4 on the control board MCU) is normally low, 8T is 0 volts. When transmitting, TX goes high, Q3 turns on Q1 and 8T becomes 8 volts. RX (RD5 on the control board MCU) is normally low, 8R is 0 volts. When going into one of the CAL menu items or the ATU menu item, or between CW elements when transmitting (see my original message below), RX goes high, Q4 turns on Q2 and 8R becomes 8 volts. I haven't found a description of any of these signals anywhere, but it looks like TX and RX are MCU outputs; that TX should be high and 8T should be 8V when transmitting; and that RX should be high and 8R should be 8V when receiving. Is this correct? If I short Q2's collector and emitter to force 8R to 8V, or short Q4's source and drain to turn Q2 on and make 8R go to 8V, then the S meter starts acting normally, but I get no audio out - so I may have more than one problem. /MUTE maybe? I tried monitoring /MUTE with my scope, but putting a scope probe on that pin mutes the audio when the receive is on - the scope appears to be loading the circuit somehow. Floating pin? Assuming TX and RX are indeed MCU outputs, and that RX does get asserted under certain conditions, does this point to a bad MCU? Since RX *does* get asserted, I would suspect that it's *not* an issue of something pulling it low that shouldn't be. Any ideas? On Mon, 2004-06-14 at 07:20, Brian Mury wrote: > I've just completed part 2 of my K2 RF board. I seem to have a problem > on receive. I get no audio, and the S meter is reading maximum. If I > select any of the CAL menu items or the ATU menu item, the receiver and > S meter work normally. As soon as I exit the menu, it goes back to no > audio and the S meter reading max. I can also receive between elements > when keying. > > Anyone have any ideas what to check? -- 73, Brian VE7NGR _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net http://mailman.qth.net/mailman/listinfo/elecraft You must subscribe to post. Subscriber Info (Addr. Change, Unsub etc): http://mailman.qth.net/subscribers.htm Elecraft page: http://www.elecraft.com
