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Time to add some extra kick to my K2-10; but, of course, problems arise along the way:
I find that U1 pin 2 to ground is only 5 kohms rather than > 10K. I can find no solder bridges or misplaced components. Resistors R24 and RP1 show the correct values. Should I suspect that Q10 is shorted? Other pins on U1 give correct resistances. U4, pin 8 shows a resistance of only about 2.8K rather than the expected >10K. (As directed, the +ve lead of the meter is on pin 8, -ve lead to ground.) The circuit diagram suggests that this is to be expected since the measurement is made through two forward-biased diodes (D7 and D8) to ground. Reversing the meter leads gives the expected high value of resistance. Voltage tests as indicated on p 26 of the manual give expected voltages with only 300 ma total current (20 ma increase over the K2 alone). Joe Carney, KB3FBR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Joe,
It is entirely possible that your ohmmeter is using polarity that is different than normal for DMMs. You *are* using a DMM are you not? If you are using a VOM or VTVM, stop - the voltage used in those meters (ohmmeter function) may be high enough to saturate semiconductor junctions and possibly cause damage. If you do have a DMM, try the U1 pin 2 resistance with reversed leads. 73, Don W3FPR On 1/23/2014 11:23 AM, MARY HAYS CARNEY wrote: > Time to add some extra kick to my K2-10; but, of course, problems arise along the way: > > I find that U1 pin 2 to ground is only 5 kohms rather than > 10K. I can find no solder bridges or misplaced components. > Resistors R24 and RP1 show the correct values. Should I suspect that Q10 is shorted? Other pins on U1 give correct resistances. > > U4, pin 8 shows a resistance of only about 2.8K rather than the expected >10K. (As directed, the +ve lead of the meter is on pin 8, -ve lead to ground.) The circuit diagram suggests that this is to be expected since the measurement is made through two forward-biased diodes (D7 and D8) to ground. Reversing the meter leads gives the expected high value of resistance. > > Voltage tests as indicated on p 26 of the manual give expected voltages with only 300 ma total current (20 ma increase over the K2 alone). > > Joe Carney, KB3FBR > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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