John, I suspect you created a base to emitter short on Q7 - it only takes a millisecond or so for the transistor to be destroyed. You can remove T3 which takes the +12 volts off the Q7/Q8 transistors and see if everything else is normal (of course, there will be no RF output).
If removing T3 fixes most everything, order the K2PAKIT from Elecraft. 73, Don W3FPR On 10/24/2010 9:08 AM, [email protected] wrote: > Hi All, > > K2 #6998 has had a short life. Working perfectly with KSB2/KDSP2/KNB2 all > installed until tonight. > > I decided to tweak one of the BFO settings, connected the frequency counter to > the control board and was about to connect it to the BFO test point on the RF > board, when I dropped the tip into the vicinity of Q6/Q7 - can't say exactly > where it landed, but I heard a click and the K2 went dead. I waited a few > minutes and powered up again, thinking the resetting fuse might have tripped. > Now the K2 starts, the Elecraft initialisation appears, the frequency readout > appears, and by this time (3 seconds or so) the self-resetting fuse gets hot > and > the K2 shuts down. > > I guess I have a short. No visible evidence of where - I took the K2 apart > to look. > > Resistance tests on the front board and control boards are all OK. > > Resistance tests on the RF board are no longer normal: > > Q7 base resistance to ground = 538ohm (ref 2.5 - 3.0kohm) > Q7 collector resistance to ground = 400ohm ( ref> 500ohm) > > > Other measurements: > > Q6 base resistance to ground = 119 ohm, collector 475 ohm, emitter short to > ground > > Q8 base resistance to ground = 538ohm, collector 473 ohm, emitter short to > ground. > > I'd be grateful for any advice how to proceed from here. > > > This is in the category of bad things to happen! And the KPA100 is nearly > finished :( > > Thanks and 73, > > John > VK7JB > > > > > > > ------------------------------------------------------------ > This email was sent from Netspace Webmail: http://www.netspace.net.au > > ______________________________________________________________ > 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 > ______________________________________________________________ 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
