Yes you are missing something. The power supply was first switch on, then the K2. At switch on the capacitors into the K2 charges themself, and the power supply answered to this by emiting spikes. I never write that all power supply have the same behavior, but for mine, it explained the K2 PA transistors failure. A scope showed clearly the problem with this power supply. After changing the power supply, I had no more PA transistors failure.
Georges F6DFZ Am I missing something here? Seems to me that the rational thing to do is turn on the power supply and let it stabilize (should only take a second or two), then turn on the K2/K3? Turning a K2 or K3 on and off using the power supply switch never gives the firmware/software a chance to initialize or shut down...just like pulling the plug on your computer might well cause at least mild consternation to the machine! There are no enormous filter caps in either Kn machine that need to be serviced at power on. Seems to me that using a non-matched pair of transistors is much more likely to be the cause of failure, as someone has already pointed out. John Ragle -- W1ZI ===== On 2/17/2011 2:31 AM, Georges Ringotte F6DFZ wrote: > Hi to the group, > > When I had my K2/10, I had multiple failures of the PA transistors. > Close investigation showed that the problem came from my switching power > supply (a professional 5A one from Friwo). > When switching on the K2, the power supply emited large spikes that > destroyed the PA transistors. > If the K2 was first switched on its internal battery, and then the power > supply was switch on, no problem as the capacitors of the K2 were already > charged. > > Before restauring your K2, check your power supply with a scope at switch > on. > > Best regards. > > Georges F6DFZ ______________________________________________________________ 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
