RE: [Elecraft] KPA100 Problem still exists, but some new measurements
Gerhard, That small negative voltage may be coming from the AC ripple on the '90-150 V' supply to the TR switch that is being coupled through the RF chokes and capacitors into the Q1 and Q2 collector circuit and then being rectified by the transistors themselves. If that is the case, it may not be a problem at all once you connect a +12 volt supply. Put an RF probe on the cathode of D13 and see how much RF voltage is present there (it would be at the approximate frequency of X1). 73, Don W3FPR -Original Message- Hi there, I'm still on page 43 in the process and I have now narrowed the problem area. You remember, I measured a negative voltage of 0.15V on J3+. Now: I removed Z1 and found the voltage measured at the collectors of Qs 1 and 2 to be -0.4V (J3+ is ok now). I don't know where it could come from. Shorting the collectors to ground via 1k resistor it takes 3 seconds to eliminate the voltage. I measure 0V. Removing the resistor it takes abt. 20 seconds for the voltage to go to -0.4V again. T2-4,5 are ok. The base of the transistors are ok, 0V. The emitters also, 0V. The body of T2 also has -0.4V. Any idea and testing procedures appreciated! ___ 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
Re: [Elecraft] KPA100 Problem still exists, but some new measurements
G'day, Did you have a light shining on the PA transistors? J3+ on my KPA100 had -0.18V. Apparently something to do with illumination of the PA's. Well noted by others. Regards, Mike VP8NO - Original Message - From: Gerhard Schwanz [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Friday, February 04, 2005 10:42 AM Subject: [Elecraft] KPA100 Problem still exists, but some new measurements Hi there, I'm still on page 43 in the process and I have now narrowed the problem area. You remember, I measured a negative voltage of 0.15V on J3+. Now: I removed Z1 and found the voltage measured at the collectors of Qs 1 and 2 to be -0.4V (J3+ is ok now). I don't know where it could come from. Shorting the collectors to ground via 1k resistor it takes 3 seconds to eliminate the voltage. I measure 0V. Removing the resistor it takes abt. 20 seconds for the voltage to go to -0.4V again. T2-4,5 are ok. The base of the transistors are ok, 0V. The emitters also, 0V. The body of T2 also has -0.4V. Any idea and testing procedures appreciated! Kind regards Gerhard Schwanz DH3FAW mailto:[EMAIL PROTECTED] http://www.gs-personal.de ___ 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 ___ 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
Re: [Elecraft] KPA100 Problem still exists, but some new measurements
Well, um, yes. And I noticed another thing which led me think everything is fine. The voltage was there, even without power connected to the K2 at all. All is well now, I neglected the voltage. I will go on air tomorrow for on air tests. RS232 test is next now, then shield and final assembly. And thanks to all who helped!!! Gerhard Schwanz DH3FAW mailto:[EMAIL PROTECTED] http://www.gs-personal.de - Original Message - From: Mike Harris [EMAIL PROTECTED] To: Gerhard Schwanz [EMAIL PROTECTED]; Sent: Friday, February 04, 2005 5:14 PM Subject: Re: [Elecraft] KPA100 Problem still exists, but some new measurements G'day, Did you have a light shining on the PA transistors? J3+ on my KPA100 had -0.18V. Apparently something to do with illumination of the PA's. Well noted by others. Regards, Mike VP8NO - Original Message - From: Gerhard Schwanz [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Friday, February 04, 2005 10:42 AM Subject: [Elecraft] KPA100 Problem still exists, but some new measurements Hi there, I'm still on page 43 in the process and I have now narrowed the problem area. You remember, I measured a negative voltage of 0.15V on J3+. Now: I removed Z1 and found the voltage measured at the collectors of Qs 1 and 2 to be -0.4V (J3+ is ok now). I don't know where it could come from. Shorting the collectors to ground via 1k resistor it takes 3 seconds to eliminate the voltage. I measure 0V. Removing the resistor it takes abt. 20 seconds for the voltage to go to -0.4V again. T2-4,5 are ok. The base of the transistors are ok, 0V. The emitters also, 0V. The body of T2 also has -0.4V. Any idea and testing procedures appreciated! Kind regards Gerhard Schwanz DH3FAW mailto:[EMAIL PROTECTED] http://www.gs-personal.de ___ 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 ___ 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
Re: [Elecraft] KPA100 Problem still exists, but some new measurements
Now: I removed Z1 and found the voltage measured at the collectors of Qs 1 and 2 to be -0.4V (J3+ is ok now). I don't know where it could come from. Hi Gerhard: Dunno if this is related, but I got a small voltage J3 by shining a bright light on the final transistors. There is some sort of photoelectric effect. Your numbers are close to what I measured then: http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-11/msg00574.html -- Ward ___ 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
