Re: [Elecraft] K2 Control Board Issue
Glenn, R7 has no association with the voltage display - it does however have a lot to do with the current display. The voltage detection is done by the voltage divider consisting of R9 and R10 on the control board. The voltage measured at the junction of R9 and R10 (or U3 pin 5) should be 20% of the 12 volt input (as measured at P7 pin 2). I would wager you have a bad solder connection at R10. Measure the resistance from U3 pin 5 to ground - it should read 196k. As for R7 reading zero ohms, I would suggest you look for a solder bridge. If you find none, then remove U6 and remeasure. Should the R7 resistance come up to normal, then U6 will have to be replaced - and be careful about taking proper anti-static measures. Is there any chance you are using an old VOM or VTVM to check resistances? If so, know that those can cause solid state devices to conduct and may even cause damage. Use a DMM - those do not use high voltages for resistance measurements. 73, Don W3FPR On 5/9/2014 1:14 PM, Glenn Haffly wrote: Doing something I should have not done , I managed to blow up Q11on the control board. I fixed that with a replacement from my junkbox. All voltages are correct on control board U3. When tapping display I get a voltage of 23.3 volts indicated from a 12 volt supply and zero current. Further checking shows R7 on the control board is zero ohms instead of 1.78K. How important is it to replace R7 with a 1% resistor rather than something from the junkbox? Everything else on the K2 works fine , TX and RX are OK. Hopefully a replacement R7 will then display the correct voltage and current. Any input from the reflector is appreciated. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] K2 Control Board Issue
Resistors almost never fail shorted, I've never seen it happen. Check for solder bridges, and look at the schematic and see what else could be causing a 0ohm reading. 73, Ross N4RP On 5/9/2014 1:14 PM, Glenn Haffly wrote: Doing something I should have not done , I managed to blow up Q11on the control board. I fixed that with a replacement from my junkbox. All voltages are correct on control board U3. When tapping display I get a voltage of 23.3 volts indicated from a 12 volt supply and zero current. Further checking shows R7 on the control board is zero ohms instead of 1.78K. How important is it to replace R7 with a 1% resistor rather than something from the junkbox? Everything else on the K2 works fine , TX and RX are OK. Hopefully a replacement R7 will then display the correct voltage and current. Any input from the reflector is appreciated. Glenn , K5ZE __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to n...@n4rp.com -- FCC Section 97.313(a) “At all times, an amateur station must use the minimum transmitter power necessary to carry out the desired communications.” __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] K2 Control Board Issue
Doing something I should have not done , I managed to blow up Q11on the control board. I fixed that with a replacement from my junkbox. All voltages are correct on control board U3. When tapping display I get a voltage of 23.3 volts indicated from a 12 volt supply and zero current. Further checking shows R7 on the control board is zero ohms instead of 1.78K. How important is it to replace R7 with a 1% resistor rather than something from the junkbox? Everything else on the K2 works fine , TX and RX are OK. Hopefully a replacement R7 will then display the correct voltage and current. Any input from the reflector is appreciated. Glenn , K5ZE __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
