Don, Yours has been the only reply though I did talk to Richard at Elecraft. The setup for the test is no antenna, no xmit, no other cables connected other than the 4 inch cable from K2 P4 to KPA 100 P1. I reheated the offending pins and double checked the components in that circuit for good soldering, no bridges and correct values on resistors and caps. I just rechecked and nothing has changed, i.e., U5 pin 1 @2.4v and U6 pin6 at 28v...I followed the schematic thru the VRFDET and found that J8 (aux I/O) pin 7 has 28v as does P1 (to Ctrl Board) pin 10 has 28v. Any suggestions? 73 Tom
-----Original Message----- From: Don Wilhelm [mailto:[EMAIL PROTECTED] Sent: Wednesday, July 21, 2004 3:02 PM To: [EMAIL PROTECTED]; Elecraft Subject: Re: [Elecraft] KPA100 voltage measurements? Tom, I have not yet seen a reply on the reflector to your questions, so I will try to give you some information. The voltage at U5 pin 1 will depend on the reflected voltage sensed by D17 and the setting of R27 - if you are measuring the voltage under transmit conditions, do you have a good dummy load connected? Pickup on an antenna wire connected to the output MIGHT do strange things during receive periods too. You should have the same voltage on U5 pin 1 and pin 3 because U5A is a unity gain op amp. If the voltage on pin 1 is much different than the voltage on pin 3 the problem will be found after the op amp U5A, but if they are the same, the problem is in the SWR bridge or its adjustments. I am at a loss to explain 28 volts on U6 pin 6 - that is another op amp and it is powered from a 5 volt supply, so the pin 6 voltage will never be brought higher than 5 volts by anything in U6 itself. A regular RS232 computer cable plugged into the KPA100 and connected to a computer might cause that kind of voltage - DO NOT USE A REGULAR COMPUTER SERIAL CABLE - BAD THINGS WILL HAPPEN. Check for something tied into the VRFDET line somewhere in the base K2 or on the KPA100 board's AUX IO umbilical cord and/or the DB-9 connector. Follow the PC board traces from U6 pin 6 to the connection with the cable and the DB-9 connector for a short to an adjacent trace or solder pad. That is all I can tell you with the info I have right now. 73, Don W3FPR ----- Original Message ----- > > Am on page 23; KPA100 test points and have two problems: > > U5 Pin 1 should be 0 to 0.1; I get 2.4 > > U6 Pin6 should be 0 to 0.5; I get 28v! > > Any ideas or where to look? All other measurements were either right on or > within the +/- 10%. > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
