Hi Don and Gary, Thanks for the quick replies and you both nailed it. U6 pin1 was being pulled down by a solder bridge on the thermistor board between the lower pad of the thermistor and left pad of R-D. Strand of solder no more than 1/10th the thickness of a hair. Even with the magnifier I wasn't entirely sure it was there, but it vaporized when I hit it with the iron. Now have a nice 13.1Khz differential between the high and low references. Appreciate the help. I'm sure I'll be back for more!
73 de Gil Ab1jv -----Original Message----- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: Thursday, June 17, 2010 9:07 AM To: Gil Bishop Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 PLL Reference Osc. Range Test failed Gil, Your troubleshooting should start in the middle. Monitor the voltage at RF board U5 pin 7 while in the CAL FCTR menu. You should see 4 volts there when you tap BAND+ and zero volts when you tap BAND-. If that does not happen, your problem will be found bact toward the microprocessor, but if the voltages are as expected, your problem lies in the forward direction, perhaps on the Thermistor board. Next check is at RF Board U6 pin 1. That should go to 8 volts when BAND+ is tapped and to near zero with BAND-. If that check fails, look for the problem on the thermistor board - usually a solder bridge - you can reach the back of the board if you remove the control board and front panel. If the test is OK, then move forward - check the soldering of R19, RP3 and D16 and D17, then monitor the voltage at RP3 pin 1 while doing the BAND button taps , repeat at RP3 pin 3. If you have a change from 8 volts to zero volts there, all should work - check the frequency at TP3 when tapping the BAND buttons. Report your progress (or lack thereof). Tell us where it works and where it does not. 73, Don W3FPR Gil Bishop wrote: > Hi all, > Just finished part II of the RF board assembly. (If it makes any > difference, this is a ~6-year old never opened kit that I'm assembling, ser > #5441, with the thermistor board mod and the PLL stability mod on the bottom > of the board). PLL reference OSC stable at 12084.34Khz when in CAL FCTR > mode and probe at TP3. But no deviation at all when using BAND+/- to check > range. Haven't started to dive in yet - that's for tonight. Would > appreciate suggestions on how/where to logically start troubleshooting this. > > 73 and thanks! > Gil ab1jv > > ______________________________________________________________ > 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 > > ______________________________________________________________ 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
