Very many thanks to everyone who responded to my request for help. Happily the fault turned out to be something very simple. Rob at Elecraft suggested the LPA FETs may have failed as the current measurements I had taken indicated the FETs were not drawing the bias current they should be. I checked the voltage on the FETs on the LPA module and found it to be 6.5V. Looking at the circuit diagram this should have been 12V as the supply to them comes directly from the 12V supply. I noticed the 12 pin edge connector on the module did not seem to be fully seated. I eased it into place, the FET voltage returned to a solid 12V and the rig is now functioning normally.
Again thanks to everyone who replied. 73, Peter, G4BVH On 6/15/2020 4:04 AM, G4BVH wrote: > Hi, > > > > I have had a fault develop on my K3 whereby there is no RF being produced. I > have emailed the details to Elecraft support and am hoping to receive a > reply with suggestions. However, I thought I would also send the details > here in case anyone can suggest something to try or investigate further. > > > > I have a K3, serial number 6482 which I built from a kit. It has worked > flawlessly since I built it. I have the 400Hz and 2.7kHz (2.8kHz?) filters > fitted and the 100W module but no other additions. > > > > A few days ago, it was running 20W of FT8 and I suddenly discovered that it > hadn't been transmitting. Everything appeared that it should be > transmitting: the red TX LED was lit, it was not in TEST mode (TX not > flashing) but there was no RF output displayed on the bar graph and > definitely nothing coming out on any mode. There is no RF if I wind down the > power below the 10W level, there is the usual relay click going through 12W > - 13W and still no RF above this level, ie on towards 100W. > > > > The K3 metering shows 13.5V and 0.84 on receive, 0.97A on the lower power > level setting and 1.18A on the higher power setting on transmit. The RF > output bar graph always displays 1 bar on transmit no matter what the power > level is set but there is no RF coming out. > > > > I tried the TX calibration but it fails saying the power level didn't reach > that required. > > > > The receiver works fine and I can hear the CW side tone and SSB, AM and FM > audio monitoring as normal. > > > > I have removed and reseated the front panel and also the 3 coax patch leads > behind the front panel but this made no difference. There is a yellow LED, > D33, on the main board which is lit on receive and goes out on transmit. > > > > The latest firmware is installed - I updated this a month or so ago. > > > > TX inhibit is OFF and the 20A breaker has not tripped. > > > > Any thoughts or suggestions gratefully received. > > > > Very many thanks and 73, > > > > Peter, G4BVH > > > > > > > -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ______________________________________________________________ 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 g4...@cathyandpeter.com ______________________________________________________________ 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 g4...@cathyandpeter.com ______________________________________________________________ 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
