Two things. First, I want to say again how much I appreciate not just this reflector, but more so the people who participate in it. Last night, within 20 minutes I had six replies from, literally, across the globe, every one of them encouraging and helpful. Thanks, guys.
Second, for anyone who likes solving puzzles, I am reprinting below my recent off-list message to Don Wilhem, W3FPR, to whom the rig will be going for further investigation. Submit your diagnoses and I’ll let you know what Don discovers once he actually has the rig on his bench. No prizes available, but it might be fun . . . Here’s the latest status report: ___________________________________________ This morning the symptoms remained: No LCD light, popping noise in speaker, voltages at either side of F1 were 14 with power switch off and essentially zero with power switch on. The same on both sides of D10, and the same at the accessory DC power pins. Resistance from Q7 and Q8 cathodes to ground was about 2 ohms. 1. Removed control board and front panel board; tested RF board alone — same symptoms (low resistance and apparently a short somewhere on the 13 VDC line.) So those boards weren’t the problem 2. Reassembled everything and then removed the heat sink. Resistance measurements at Q7 and Q8 unchanged. Examined thermal pads, checked shoulder washer placement and all associated hardware. No changes – still low resistance from collectors to ground. 3. Reassembled and tried it again. No change – no lights, popping noise in speaker, voltages as in step 1 above. 4. As a last ditch effort, decided to change power supplies (had been using an MFJ rated at 40 watts.) Made up a cord to connect K2 to a known good supply with a built-in ammeter. I thought I’d be able to see a current spike if there was a short, as F1 opened and closed. The K2 came to life and the current draw was nominal (less than 200 mA.) Switched back to the MFJ supply. That worked too. Problem solved? No. See number 5. 5. Decided to see if it really was cured. Connected K2 to a known good dummy load, through an SWR meter. Keyed it with power set to 10 watts – but the forward power needle set for full scale barely nudged. Checked the power output as read by the K2’s onboard power meter. It read 0.5 watts, no matter where the power control is set. Confirmed that current maximum in the configuration menu was set at 3.5. It was. Tried the same routine with a known good antenna connected (measured SWR at less than 1.2:1) Same results. I don’t know what all this means, but I am going to take a wild guess. Last night something – maybe Q7 or Q8 but maybe something else – developed an internal short at exactly the instant I did a direct frequency entry of 10.000 Mhz (a relay clicks at that point). This morning, for whatever reason, when I changed power supplies, I am guessing that whatever had been shorted (or nearly so) burned out, creating an open circuit where there had been a low-resistance fault. Since the rig is producing 0.5 watts but not more, that makes me think it may be one of the output transistors. Note that, until last night, it happily produced as much as 15 watts. In any case, the rig came out of its coma but now it can’t speak. And maybe it can’t hear. Tthe receive function also seems to have been degraded – I heard no signals when the antenna was connected – though I can check that further by using the K3 to see if anyone is on the bands and comparing it to the K2. So, what do you think is going on? Ted, KN1CBR ______________________________________________________________ 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]
