I'd suggest to replace the toroid core, as the high temperatures to which it was subjected may have altered the characteristics of the material.
73, Matt VK2RQ > On 1 Jul 2014, at 12:40 pm, "Mike Lewis" <[email protected]> wrote: > > So brought the K3 in to work this morning to our lab area where we have > static benches, blowers, wrist straps etc. and opened it up. Sure enough, > the T4 transformer was pretty crispy looking. My boss who is also an avid > ham (dream job setup :) ) then sprang into action. He removed the > transformer, counted the turns, removed the old wire, found some new magnet > wire of the proper gauge, rewound the toroid, and replaced both it and the > straight through portion (which had gotten pretty hot from the proximity to > the core.) Prior to stripping the burned turns off of T4 we looked at it > under a microscope and saw that the windings had burned open in one place, > effectively acting as a fuse of sorts. There didn't seem tpo be any other > parts, connectors, or board traces that looked to have been stressed. I > brought the radio home and hooked it up to a dummy load and a reasonably > accurate external wattmeter. It seems to be fine, both on receive and > transmit. > > > > I was hoping there was a built in SWR bridge cal procedure, but I didn't see > anything like that in the manual. The SWR values reported though seem to > match the LP-100A I am using externally pretty closely. I did try to follow > the Wattmeter calibration and ran into some confusion on the procedure as > written in the manual. I think I was able to puzzle it all out except for > one item - how do you change the config menu item from CONFIG:WTMR LP to > CONFIG:WTMR HP? It doesn't seem to change just by having the tune power > changed to 50 watts, so I am at a loss on how to change it. > > > > So perhaps my K3 is now alright again, although I would appreciate any other > comments on other things to check or calibrate. And thanks to all on the > list who helped me out. After this the next project is to fuse the DC supply > cables to my DC blocks with some rationally small value of fast blow fuse :) > > > > de Mike/KE0MF > > ______________________________________________________________ > 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] ______________________________________________________________ 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]
