Don, thanks for the help, at least I think we are getting close to solving this mystery to me. I can converse with you on tubes, but this solid state stuff is new to me. Shows you how old I is.
Pin 1 of U1 has 6 volts present and will not go to zero as you suggested. Pin 3 of U1 reads zero. As you indicated that is my problem. Following the steps in the manual and your advice I was able to get the high reading of 12101.18 and the low 12091.42. The following voltages are: U6, Pin 1 high 7.64v and low 11.4 microvolts (?); U6 Pin 3 high 4.06v and low 11.4 microvolts. I measured Pin 20 of U6 to be 6 volts. I lifted R19 and the readings were 4.08 before and 7.64 afterwards. I removed the thermistor board and checked the resistors and found no errors. I examined the board around the thermistor and found no solder bridges as you suggested I might have. Anyway, I think you are about to resolve my issues to which I appreciate. Dwight W4IJY K2 #4766 -----Original Message----- From: Don Wilhelm [mailto:[EMAIL PROTECTED] Sent: Monday, August 21, 2006 10:32 PM To: C Dwight Baker Subject: RE: [Elecraft] Alignment & Test II Dwight, The real problem is that U1 pin 1 is not going to zero. Now take a tiny step to try to discover the cause - do the same test of the PLL range (you can ignore the frequencies for this), but check the voltage at U6 pin 3 when the BAND+ button is tapped and also when the BAND- button is tapped. We want to see the voltage at pin 3 go from about 4 volts to about zero volts. If you do get the 0 to 4 volt swing at pin 3, then the firmware and DAC are doing the job properly, you will find the problem on the thermistor board, and the most likely is a solder bridge between pins 5 and 6 - the pads get quite close to each other there and a solder bridge is easy to create. The 0 to 4 volt swing at U6 pin 3 should make the voltage at U6 pin 1 swing from 0 to 8 volts if the resistors in the op amp circuit (mainly the thermistor board) are correct. If you need to convince yourself that the pin 1 output is not being loaded down, just lift one end of R19 and repeat the test. U6 should have twice as much voltage on pin 1 as is put onto pin 3 when all is well with the resistor network. 73, Don W3FPR > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of C Dwight Baker > Sent: Monday, August 21, 2006 8:52 PM > To: [email protected] > Subject: RE: [Elecraft] Alignment & Test II > > > Don, I followed your suggestions and I am still at the same place > I started. > > > I began by following the schematic as you suggested and marked each > component as I verified the correct values and type. I found no > errors (at > least I didn't but it doesn't mean I erred again). > > It appears I had a solder bridge between pins 4 and 5 on U6. I > replaced D16 > veractor MV209 and did not have another D17 ISV149 so the old one is still > there. > > The readings remained virtually the same as before. The voltages > at U6 pin > 1 were as follows: High 12103.15, voltage 7.61; low 1209.03, > voltage 3.74. > > Pin 8 of the thermistor board was 7.97 and pins 6 and 7 measured > 3.96. Pin > 1 measured 7.64. The line voltage at the power plug was 14.3 volts. > > I am curious why the voltage on the lower reading did not go to near zero. > Would Q19 (J310), D17 be faulty and what effect does U4 have? > > I appreciate your time for leading this BOOF (burnt out old f-rt) through > the dark. > > Thanks again, > > Dwight W4IJY K2 4766 > -----Original Message----- > From: Don Wilhelm [mailto:[EMAIL PROTECTED] > Sent: Monday, August 21, 2006 9:17 AM > To: C Dwight Baker; [email protected] > Subject: RE: [Elecraft] Alignment & Test II > > Dwight, > > Don't be concerned about the setting of C22 until after you have finished > the entire build - just set it to mid-position for now. You will want to > re-do CAL PLL and CAL FIL after you are done with the 4 MHz oscillator set > precisely to achieve good dial calibration. The K2 does not use the 4 MHz > oscillator on a real time basis, only during CAL PLL and CAL FIL > operations. > > Now in to your problem. Yes, your PLL high and low frequencies > are too high > and the range is too small. > Turn your manual to the back and find the schematic for the RF > Board - sheet > 1. Then find the area in the left upper corner marked PLL Reference > Oscillator. Check all the components associated with that circuit, > especially the capacitors, varactors, and inductor L31 for proper > values and > make certain they are in the correct holes. Re-verify that D16 > and D17 are > correct - D16 is the larger bodied varactor and D17 is the smaller. > > After verifying the components above, go back to CAL FCTR with > the probe in > TP3, tap the BAND+ button and read the high frequency, then measure the > voltage at U6 pin 1 (it should be near 8 volts). > Then tap the BAND- button and read the low frequency and measure > the voltage > at U6 pin 1 (now should be near zero volts). > > Did you obtain a correct frequency range? Did the voltage at U1 > pin 1 change > from 8 volts to 0 volts? > Let us know what you find. > > 73, > Don W3FPR > > > > -----Original Message----- > > > > When I did the PLL reference oscillator range test and at 4 MHz; the > > readings are 12104.45 on the high end and 12099.20 at the low end for a > > difference of 5.25 whereas the manual indicates the range should be > > somewhere between 9.8 and 15 kHz. > > > > > > > > Adjusting C22 on the control board gives me a difference of 5.5 kHz. > > > > > > > > Where or what am I looking for or better yet have I goofed in > > populating the > > board? Phase I testing was good. > > > > > > > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.405 / Virus Database: 268.11.4/424 - Release Date: 8/21/2006 > > _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
