Dear all, Please find my emails to Elecraft support below. Is there maybe somebody with additional tips?
Thanks!! 73 Koert PA1KW ----------------------------------------------------- Hi Gary, Sorry for my late response, but I had not the opportunity to work on this earlier. I moved houses and that took longer than expected. I did check the HV bias and that is 135volts. The diodes are ok and the voltage on TP4 2mV on receive and 240mv on transmit (tune). I did connect a good dummyload close to the KPA100. I did the re-adjustment of the SWR bridge but this provided me not the required results. The best results with adjusting C1 on 5 Watts is: 160m 1.8-1 80m 1.3-1 40m 1.0-1 30m 1.0-1 20m 1.0-1 18m 1.0-1 15m 1.0-1 12m 1.0-1 10m 1.0-1 Please help...... Best regards and 73, Koert Wilmink PA1KW PS. All the best for 2008!! Gary Surrency wrote: > > Did you check to see that the HV bias at the left side of R11 is at least > > 100VDC, and the higher it is - the better? I like to see 120-150VDC > > there. > > Too little HV bias, or a damaged diode or error in the t-r switch, can > > allow > > too much RF to leak through the t-r switch when in transmit at high > > power. > > That can cause the KPA100 PA stage to self-oscillate and produce HI > > CUR and > > high SWR. The problem will be worse on the lower bands from 160m to 30m, > > since the RF transistors have higher power gain at lower frequencies > > and the > > KPA100 typically will produce higher RF output on the lower bands. > > > > If damage has occurred to the MAX1406 RS232 IC, or to any of the parts in > > the KPA100 t-r switch, it may load down the HV bias too much or allow too > > much RF leakage through the t-r switch to provide the needed input to > > output > > isolation. > > > > You must see a low null voltage at TP4 of less than 10 millivolts (on > > 40m or > > 80m) when a good 50 ohm dummy load is connected as closely as possible to > > the KPA100's antenna connectors. Do not have a SWR meter, wattmeter, coax > > switch, or long cable inserted between the dummy load and the antenna > > connector on the KPA100. Most rigs will null down to about 1-3 millivolts > > with a very close and direct connection to the dummy load. Also, the > > flange > > of the SO-239 antenna connector should be installed so it is on the rear > > panel, not on the inside. > > > > > > If the antenna was left connected when there was a thunderstorm nearby, > > lightning can damage the 1N5711 diodes in the KPA100 SWR sensors. > > > > If the diodes are OK, there should be about 98-100K ohms between their > > cathodes and ground when tested with an ohmmeter. You can do this at the > > side of the trimmer pots that connect to the diodes too. Connect the > > postive ohmmeter lead to the cathode, and the negative lead to a ground > > point on the tuner. > > > > Then, if your meter has a diode test function, there should be about > > 0.38 to > > 0.40VDC of diode drop across the 1N5711 diodes, with the + lead to > > anode, - > > lead to the cathode. > > > > The diodes are easier to replace if one lead is clipped. It can be > > done from > > the top of the PCB without removing the heat sink, if you are very > > careful, > > have good desoldering tools and skill, and you pretrim and form the > > leads on > > the new diodes. Leave a little extra lead length above the PCB for easier > > soldering. > > > > Also check to see if the calibration of the null cap, and the FWD and > > REFL > > cal pots still check out OK. > > While the PA shield is off of the KPA100, be sure to check the > > tightness of > > the screws in PA transistors Q1, Q2 as they do tend to loosen. > > > > > > > > -- > > 73, Gary AB7MY > > ========= > > [EMAIL PROTECTED] > > Elecraft Technical Support > > > > > > > > -----Original Message----- > > From: Koert Wilmink [mailto:[EMAIL PROTECTED] Sent: Tuesday, July 03, > > 2007 1:26 PM > > To: 'Gary Surrency' > > Cc: 'CSinfo' > > Subject: RE: PA1KW: RE: High SWR on 160M and 80M with dummyload > > > > > > Hi Gary, > > > > Yes I have the new value of C31 installed. It is impossible to lower SWR > > reading with C1. Other bands are perfectly working well. Any other > > suggestions? > > > > 73 Koert PA1KW > > > > -----Oorspronkelijk bericht----- > > Van: Gary Surrency [mailto:[EMAIL PROTECTED] Verzonden: Monday, > > July 02, 2007 8:34 PM > > Aan: 'Koert Wilmink' > > CC: 'CSinfo' > > Onderwerp: PA1KW: RE: High SWR on 160M and 80M with dummyload > > > > Koert, > > > > Is C31 in the KPA100 t-r switch the new value of 0.22uF, 63WVDC? This > > change > > is specifically to address oscillation and high SWR problems on the lower > > bands of 160m-30m if there is too much RF feedback through the t-r > > switch at > > high power. > > > > The new value of C31 (0.22uF, 63WVDC) applies only to late model KPA100 > > kits, or to older ones that have had the KPA100UPKT modifications > > installed. > > Info on that mod kit is on our website at: > > > > http://www.elecraft.com/order_form_parts.htm > > All parts requests should be sent to [EMAIL PROTECTED] for the quickest > > response. I'm not at the main office in Aptos, CA. I'm located near > > Phoenix, > > AZ and have no stock of parts here other than for doing repairs. > > > > > > -- > > 73, Gary AB7MY > > ========= > > [EMAIL PROTECTED] > > Elecraft Technical Support > > > > -----Original Message----- > > From: Koert Wilmink [mailto:[EMAIL PROTECTED] Sent: Sunday, July 01, > > 2007 2:08 AM > > To: [EMAIL PROTECTED] > > Subject: High SWR on 160M and 80M with dummyload > > > > > > Dear Elecraft, > > > > I've a high SWR on 160 and 80M with my K2/100 # 5618. With a dummyload I > > cannot get the SWR meter adjusted right. I cannot get it lower than > > 1.9-1 on > > 160M and 1.7-1 on 8oM. On all other bands it's exactly 1.0-1. Any > > suggestions? > > > > 73 Koert PA1KW > > > > No virus found in this outgoing message. > > Checked by AVG. Version: 7.5.476 / Virus Database: 269.9.14/884 - > > Release Date: 7/2/2007 > > 3:35 PM > > > > > > > > > > > _______________________________________________ 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
