K1 with a strange XFIL problem...
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K1 with a strange XFIL problem...
 
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Re: K1 with a strange XFIL problem...
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Re: K1 with a strange XFIL problem...
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Re: K1 with a strange XFIL problem...
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Success!
Thanks to Bruce N1RX for his knowledge and prior troubleshooting to resolve this issue.  What he described and photographed (above) are exactly the cause of this problem. The RIT switch leg was making contact with pin 5 of J1. 72/73 Dave For further details, please see Bruce's reply to me below: Yes I had this exact problem on one I repaired in July of 2012. It was traced to a short between the RIT/XIT switch to a trace on the board, where the switch lead had been bent over by the original builder before soldering. I corresponded with Don Wilhelm about this. Though he didn't provide the solution, our conversation led me to the tests that found it. Copied below is a repost of my last message to Don, after I resolved it. I don't recall if I posted this to the reflector or not. In any event, It may help someone in the future. I have a photo of the offending switch pin connection, if anyone wants it. Bruce Beford, N1RX Hi, Don. You may recall that I posted recently to the list about a strange problem with a K1. I resolved it today, and wanted to share the results with you. Here's a copy of my original post: OK, folks. Time to put on your thinking caps... I just purchased a used K1. Has NB, ATU and 4 band board, set for 7/10.1/14/21 MHz. All appears to be operating normally, except... When cycling through the crystal filter bandwidths from FL1-FL3, once FL3 is reached, all buttons become unresponsive. The VFO readout still works, but the MCU will not respond to any key presses. The filter does actually switch to the narrowest setting, based on the audio response. Cycling the power returns the rig to normal operation (on FL1), and all works fine again until trying to use FL3. About the only other anomaly I notice is what seems to be a louder pop in the speaker when switching in RIT or XIT than I remember from my last K1. I have not yet begun any troubleshooting (except for a full reset). Just thought I would poll the collective wisdom here before digging in. Actually, I'll be getting ready for Lobstercon over the next couple of days, so I don't know how much time I'll be able to commit until after the weekend. ---------------------------------------------------------------------------- You and I both suspected a problem with the MCU, as there should no other circuitry involved, except the DAC and EEPROM. You also suggested perhaps replacing those ICs while in there. Fortunately, I have a friend who allowed me to borrow his working K1. Swapped the entire Front Panel board, mine works fine with his board. I then took his MCU chip and put it in my board, still have the problem. So, the problem was on my FP board, but not the MCU. One thing I did notice was a ticking noise in the audio with no antenna connected, almost like ignition noise in a vehicle, when using my board FP board but not when using my friend's. The ticking would disappear when I went to FL2. Ahh, another clue... I then decided to remove the DAC from my board and see what happens. Lo, The unit would now switch properly, FL3,FL2,FL1 and back to FL3 OK. Of course, it was not actually switching the filter bandwidth with the DAC out. I now had a pretty load, almost moterboating noise in the audio. I decided to ground what was the XFIL/TONE output pin of the DAC (pin 1) to see if it would quiet the audio. It did, BUT- it activated the RIT! Wait a minute- there should be no connection between the two.... but, there was. Upon extra careful inspection, I found that one lead on the RIT/XIT switch was not inserted through the board by the original builder. It was bent over, and was contacting pin 5 on J1 (the XFIL/TONE signal). The "moaterboating" I heard was actually the MCU driving the LCD pin and polling the input for the switch. This was not noticeable when the DAC was holding this line at a steady DC voltage. So, what was happening was when the DAC output it's lowest voltage for FL1 (about 1.6 volts), it would tickle the input pin on the MCU for the WPM+/FILTER switch. I believe the MCU would think the switch was being held in, therefore no other switches would work, until the unit was powered off. An original symptom (which I didn't recognize at the time) was when I noted that the RIT/XIT button seemed to generate an audio pop when used. That's because it was grounding the XFIL/TONE signal line. I reworked the switch connection, and all is fine now. I have attached a photo of the offending pin (not a good shot, but shows the connection in question). I thought you might like to hear about this one. Thanks for being a "sounding board", Don. I appreciate it. 73, Bruce, N1RX |
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