On Thu, Dec 11, 2008 at 6:59 AM, Don Wilhelm <[email protected]> wrote: > Brian, > > You have some problem with the wattmeter in the KPA100 - T4, D16, D17, R26, > R27, U5, U6 or on the VRFDET signal pathway back to the K2 control board. > > You seem to have a somewhat normal voltage variation at U5 pin 7, which (for > the moment) says everything is working through U5, but check the U6 pin 6 > output under the same conditions and also check for the same voltage at K2 > control board P4 pin 10.
I did. I think I said that in the original message (looking ...), yes, I did check and the output of U6 pin 6 is the signal VRFDET and tracks VFWD (output of U5b). It is properly present on header for the aux-I/O cable to the control board and I have verified the same voltages on pin 10 of the Aux-I/O connector on the control board. I did disconnect the Aux-I/O cable from the control board and I tested the base K2. Power output control of the K2 without the KPA100 connected is working is working properly. > Since this happened only by removing and re-installing the KPA100, be > suspicious of a solder joint that is not well soldered - those may work for > a while and then when touched can fail. I did carefully remove the PA board from the heatsink and check all connections visually and specifically all of those between U5, U6, and the Aux-I/O connector. I even rang out the connections. That is all good. I have also verified the entire path from U6 pin 6 (KPA100) all the way to pin 2 on the microcontroller, U6, on the control board. Voltage is present there and it does follow power output. So VRFDET is reaching the control board. Just for grins, I looked at the values for VRFDET coming form the K2 RF board RF output detector. They are *much* higher than what I am getting from VRFDET coming from the KPA100. At full output I have something like 3.5V on VRFDET from the K2 RF board output but only about 0.3V on VRFDET coming from the KPA100. I am thinking maybe D16? What kind of voltage should I see at the cathode of D16? I see about 1.7V at full power output from the PA. 73 de Brian, WB6RQN > > 73, > Don W3FPR > > > Brian Lloyd wrote: >> >> Our K2 was working perfectly until I opened it up, tightened the power >> transistor mounting screws, realigned the receiver, and put it back >> together. Now power output no longer follows the power setting. When set to >> a power output less than 10W, I hear the bypass relay but I get the High Cur >> display (momentarily) and the display then shows a power output of 0.3W with >> an SWR of 3.0. Output power as measured with a W1 is 20W. If I advance the >> power control, as soon as I pass the 10W point the PA comes on and the power >> jumps to 150W output. Turning the power level control fully CCW (0.1W >> setting) produces 6W of output. >> >> Looking at pin 7 of U5 on the KPA100 I can see good analog voltage that >> varies with power. I can see the value of VFWD change when the range changes >> (SCALE changes) also. I can also see varying VFWD at pin 2 of U1 so this >> does not appear to be an analog problem. >> >> FWIW, voltages at pin 2 of U1 for various power outputs are: >> >> 6W -- 0.15V >> >> 20W -- 0.30V >> >> 150W -- 0.29V >> >> At pin 7 of U5 (U5b): >> >> 6W -- 0.15V >> >> 20W -- 0.30V >> >> 150W -- 0.77V >> >> On the t-r menu item I have "8r hold" set. >> >> I do have output on VRFDET but the value only varies from about 0.3V-0.7V >> so that appears to be working also. >> >> I am planning to fly to Dominica on Friday and operate from there but I >> can't take the K2 unless I solve this problem. >> >> Suggestions? >> > _______________________________________________ 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
