K2 receive problem
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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: [hidden email] 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 |
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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: [hidden email] 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 |
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In reply to this post by Brian Mury-3
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: [hidden email] 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 |
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Not sure if my previous email made it to the list - I haven't seen it
yet, and I've had other emails not make it (while some just take a really long time to show up). Anyway, one more bit of data to add. In my previous email I said: 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? If I short Q2's collector and emitter, and pull /MUTE high (5V), then the S meter works *and* I get audio, so it looks like a problem with both RX and /MUTE not getting asserted properly. Once more, any ideas anyone has would be appreciated - I don't know *why* RX and /MUTE are behaving incorrectly. On Mon, 2004-06-14 at 23:28, Brian Mury wrote: > 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: [hidden email] 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 |
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I've found the problem. Gary at Elecraft told me that VFRDET (pin 2 of
the control board processor) is pulled low, and should be close to 0 volts when in receive - if it's not, the processor will not assert RX. After a couple email exchanges with him, I found that when I had inserted the IC into the socket, pin 1 bent over and shorted with pin 2. Straightening the pin and reinserting the IC solved the problem. My thanks to Gary, and now I can finish my radio! VRFDET input pin 2 of > the 18C452 is allowed to float, it will not assert the RX pin 28 to 5V > and the 8R line for the RX will remain off. On Mon, 2004-06-14 at 23:34, Brian Mury wrote: > Not sure if my previous email made it to the list - I haven't seen it > yet, and I've had other emails not make it (while some just take a > really long time to show up). > > Anyway, one more bit of data to add. In my previous email I said: > > 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? > > If I short Q2's collector and emitter, and pull /MUTE high (5V), then > the S meter works *and* I get audio, so it looks like a problem with > both RX and /MUTE not getting asserted properly. > > Once more, any ideas anyone has would be appreciated - I don't know > *why* RX and /MUTE are behaving incorrectly. > > On Mon, 2004-06-14 at 23:28, Brian Mury wrote: > > 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: [hidden email] 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 |
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