Hi Jerry, I had the same problem and suspected U4, I removed U4 and fitted and IC holder, and then fitted a new IC and still had the same fault.
The problem turned out to be a cracked capacitor in the voltage magnification line. The Capacitor spacing is a bit smaller than the holes provided and I had used too much force getting the component flat. There are not many conponents to check. make sure you have a good desoldering tool. 73's Andrew PS Merry Christmas Jerry and Don Don Wilhelm-4 wrote: > > Jerry, > > That means U4 is not the problem, the problem is somewhere in the > rectifier stack and goes away when you lift the anode of D7. > > Check both D7 and D8 for proper orientation (use the parts placement > diagram since the board silkscreen is covered). Check for a solder > bridge across the leads of C38. Be certain C35 is soldered properly. > If you lift the anode of D7 and place a 0.1 uF capacitor from the > "flying lead" of D7 to ground, what is the voltage at the D7 anode? > > I know that did not fully identify the failure point, but hopefully it > gives you some clues. > > 73, > Don W3FPR > > n0jrn wrote: >> Gang: I need some advise please. >> >> I'm trying to finish my KPA100 but I can't seem to get beyond voltage >> tests >> on page 46 of the manual. >> >> I should be getting 90 to 150 V's at the junction of C77 & R11 but only >> getting 47 volts. >> >> I should be getting -5 to -25 V's at pin 8 of U4 BUT I'm only >> seeing -4.1. >> >> I did some research in the archives and came up with a few ideas. >> Checked >> D1 - D8 and T3 pads. All diodes pass continuity test and T3 seems fine >> and >> shows zero resistance between pads. >> >> Checking the schematics prompted me to lift the anode of D7 to remove U4. >> In doing this, the voltage at the junction of R11 came up into spec and >> shows 150 V's. >> >> This means that U4 is drawing the circuit down. SO, I sent Elecraft an >> e-mail and Gary sent me a new MAX1406. Figured I would install >> it >> and all would be good. NOT ! >> >> After installing the new U4, I rechecked voltage at R11 and found it >> is >> still just 47 V's. >> >> I've double checked orientation of U4, and it's fine. I was very >> careful >> to observe anti static procedures when installing the new chip. SO, >> I'm >> confused and not sure where to go from here. >> >> Any advise would be greatly appreciated. >> >> Thanks & 72: Jerry N0JRN >> >> ______________________________________________________________ >> 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 >> ------------------------------------------------------------------------ >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 9.0.716 / Virus Database: 270.14.105/2562 - Release Date: >> 12/13/09 02:39:00 >> >> > ______________________________________________________________ > 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 > > -- View this message in context: http://n2.nabble.com/KPA100-problem-tp4161606p4163408.html Sent from the [K2] mailing list archive at Nabble.com. ______________________________________________________________ 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
