A Bad Thing Happened To My K2
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This evening I had a guest ham in the shack who was curious about my K2 and
asked if we could hook it up. So we did. I pointed out which 12v power strip, power cord, and antenna to use. While I was getting the proper computer interface cables hooded up, my guest connected the radio to the power and switched it on. I heard a loud snap and immediately looked in the direction of the K2 operating position. My guest had a strange look on his face and I asked what happened. There was a spark from the outside of the antenna connector on the back of the K2 to the center connector of the coax. That can't happen, right? Wrong. After shutting down the power supply and inspecting things, I discovered my guest had wired the power backwards. Fortunately the reverse polarity circuitry protected the radio and internal battery. The radio was operating from the battery, that's why it came on. I still can't understand where the spark came from. However, I now have virtually NO receive on 40m, that's where the radio was when the spark occurred. I have transmit and receive on all other bands and transmit on 40m, just no receive on 40m. That spark killed something dealing with 40m receive. It is so bad I can't even hear the local oscillator around 7000 KHz with the pre-amp on. There is no CW or SSB receive. Mark, KJ7BS Glendale, AZ Editor, The SKCC Centurion Elecraft K2 S/N 0539 Fists # 2972 CC 1806 SKCC # 2240 C56 T20 MQFD # 128 QRP-ARCI # 12647 AZ ScQRPions COGRC Emergency Communications _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: A Bad Thing Happened To My K2
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Mark,
I am puzzled since you say it transmits on 40 meters, but does not receive - and that it receives well on other bands. There is precious little in the K2 that would create that situation. What do you have set for 40 meters that is different from other bands? Preamp on/off? Attenuator on/off? RANT on/off? Do you have the K160RX installed? If so, connect your antenna to the receive antenna jack and see if the receiver comes to life. Now if you could not transmit nor receive on 40 meters, I would point to the relay in the 40 meter lowpass filter, so check 40 meter transmit again - and check all bands for the maximum power produced. Sometimes a transmit problem will not be revealed by transmitting at a low power level, but will reveal itself when the power control is cranked to maximum. Do you have the KAT2 installed? If so, try removing the KAT2 and see if you can receive 40 meters from the base K2 antenna jack. Other than those things, I am out of ideas. 73, Don W3FPR Mark Saunders, KJ7BS wrote: > This evening I had a guest ham in the shack who was curious about my K2 and > asked if we could hook it up. So we did. I pointed out which 12v power > strip, power cord, and antenna to use. While I was getting the proper > computer interface cables hooded up, my guest connected the radio to the > power and switched it on. I heard a loud snap and immediately looked in the > direction of the K2 operating position. My guest had a strange look on his > face and I asked what happened. There was a spark from the outside of the > antenna connector on the back of the K2 to the center connector of the coax. > > > > That can't happen, right? Wrong. > > > > After shutting down the power supply and inspecting things, I discovered my > guest had wired the power backwards. Fortunately the reverse polarity > circuitry protected the radio and internal battery. The radio was operating > from the battery, that's why it came on. I still can't understand where the > spark came from. However, I now have virtually NO receive on 40m, that's > where the radio was when the spark occurred. I have transmit and receive on > all other bands and transmit on 40m, just no receive on 40m. > > > > That spark killed something dealing with 40m receive. It is so bad I can't > even hear the local oscillator around 7000 KHz with the pre-amp on. There > is no CW or SSB receive. > > Elecraft mailing list Post to: [hidden email] 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: A Bad Thing Happened To My K2 - Update 1
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In reply to this post by Mark, KJ7BS
Thanks to everyone for the suggestions. Here is some more information
resulting from your suggestions. I have no measurable RF output on 40m or any meaningful RX on 40m. The RX/TX works on all other bands including 160m. I get the same RX/TX results from ANT1 & ANT2 and main. I get the same RX results on the receive ANT. Mark, KJ7BS Glendale, AZ Editor, The SKCC Centurion Elecraft K2 S/N 0539 Fists # 2972 CC 1806 SKCC # 2240 C56 T20 MQFD # 128 QRP-ARCI # 12647 AZ ScQRPions COGRC Emergency Communications -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Mark Saunders, KJ7BS Sent: Monday, September 22, 2008 10:04 PM To: Elecraft Mail List Subject: [Elecraft] A Bad Thing Happened To My K2 Importance: High This evening I had a guest ham in the shack who was curious about my K2 and asked if we could hook it up. So we did. I pointed out which 12v power strip, power cord, and antenna to use. While I was getting the proper computer interface cables hooded up, my guest connected the radio to the power and switched it on. I heard a loud snap and immediately looked in the direction of the K2 operating position. My guest had a strange look on his face and I asked what happened. There was a spark from the outside of the antenna connector on the back of the K2 to the center connector of the coax. That can't happen, right? Wrong. After shutting down the power supply and inspecting things, I discovered my guest had wired the power backwards. Fortunately the reverse polarity circuitry protected the radio and internal battery. The radio was operating from the battery, that's why it came on. I still can't understand where the spark came from. However, I now have virtually NO receive on 40m, that's where the radio was when the spark occurred. I have transmit and receive on all other bands and transmit on 40m, just no receive on 40m. That spark killed something dealing with 40m receive. It is so bad I can't even hear the local oscillator around 7000 KHz with the pre-amp on. There is no CW or SSB receive. Mark, KJ7BS Glendale, AZ Editor, The SKCC Centurion Elecraft K2 S/N 0539 Fists # 2972 CC 1806 SKCC # 2240 C56 T20 MQFD # 128 QRP-ARCI # 12647 AZ ScQRPions COGRC Emergency Communications _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: [hidden email] 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: RE: A Bad Thing Happened To My K2 - Update 1
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> I have no measurable RF output on 40m or any meaningful RX on 40m. > > The RX/TX works on all other bands including 160m. > > I get the same RX/TX results from ANT1 & ANT2 and main. > > I get the same RX results on the receive ANT. The only thing I see that is common to transmit, receive and the RX antenna and is only in circuit on 40 meters is the Band Pass Filters - particularly the toriods L1 and L2. If you had not said the RX Ant was also dead, I would suspect L25 and/or L26 in the Low Pass filter. If you have a separate antenna for 40 meters and are connecting it to the receive antenna for testing, I would also check the antenna (or tuner). > My guest had a strange look on his face and I asked what > happened. There was a spark from the outside of the antenna > connector on the back of the K2 to the center connector of the > coax. This would indicate a DC path through the secondary of the PA output transformer, (RF board), through the LPF and to the antenna connector. With +12V on the chassis (reversed power supply), I can see damage to one or both of the toroids in the LPF, damage to relay K12 or damage to the antenna system (balun?). 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Mark > Saunders, KJ7BS > Sent: Tuesday, September 23, 2008 11:51 PM > To: 'Elecraft Mail List' > Subject: [Elecraft] RE: A Bad Thing Happened To My K2 - Update 1 > > > Thanks to everyone for the suggestions. Here is some more > information resulting from your suggestions. > > I have no measurable RF output on 40m or any meaningful RX on 40m. > > The RX/TX works on all other bands including 160m. > > I get the same RX/TX results from ANT1 & ANT2 and main. > > I get the same RX results on the receive ANT. > > Mark, KJ7BS > Glendale, AZ > Editor, The SKCC Centurion > Elecraft K2 S/N 0539 > Fists # 2972 CC 1806 > SKCC # 2240 C56 T20 > MQFD # 128 > QRP-ARCI # 12647 > AZ ScQRPions > COGRC Emergency Communications > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Mark > Saunders, KJ7BS > Sent: Monday, September 22, 2008 10:04 PM > To: Elecraft Mail List > Subject: [Elecraft] A Bad Thing Happened To My K2 > Importance: High > > This evening I had a guest ham in the shack who was curious > about my K2 and asked if we could hook it up. So we did. I > pointed out which 12v power strip, power cord, and antenna to > use. While I was getting the proper computer interface > cables hooded up, my guest connected the radio to the power > and switched it on. I heard a loud snap and immediately > looked in the direction of the K2 operating position. My > guest had a strange look on his face and I asked what > happened. There was a spark from the outside of the antenna > connector on the back of the K2 to the center connector of the coax. > > > > That can't happen, right? Wrong. > > > > After shutting down the power supply and inspecting things, I > discovered my guest had wired the power backwards. > Fortunately the reverse polarity circuitry protected the > radio and internal battery. The radio was operating from the > battery, that's why it came on. I still can't understand > where the spark came from. However, I now have virtually NO > receive on 40m, that's where the radio was when the spark > occurred. I have transmit and receive on all other bands and > transmit on 40m, just no receive on 40m. > > > > That spark killed something dealing with 40m receive. It is > so bad I can't even hear the local oscillator around 7000 KHz > with the pre-amp on. There is no CW or SSB receive. > > > > Mark, KJ7BS > Glendale, AZ > Editor, The SKCC Centurion > Elecraft K2 S/N 0539 > Fists # 2972 CC 1806 > SKCC # 2240 C56 T20 > > MQFD # 128 > QRP-ARCI # 12647 > AZ ScQRPions > > COGRC Emergency Communications > > > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > 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: [hidden email] > 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: [hidden email] 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: RE: A Bad Thing Happened To My K2 - Update 1
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In reply to this post by Mark, KJ7BS
Mark,
If you have a signal generator, with your K2 switched to 40m in TEST mode you could try injecting a 40m signal at different points in the signal path between the RF input of the TUF-1 mixer and the antenna connector (antenna disconnected), starting at the mixer and working towards the antenna connector, to find out where you no longer hear the signal. This would narrow down the search for the cause(s) of your problem. If you do not hear the 40m signal when the generator is connected to the mixer's input, this would indicate that something is wrong with the LO system when the K2 is switched to 40m -but I would think an unlikely cause of your problem. If you do not have a signal generator, you could try either "scratch" tests along the signal path OR use one side of your disconnected antenna's feeder connected via a capacitor as a signal source. If you want to use the feeder please contact me off-List for some "warnings", also if you want further information about "scratch" tests. The K2 *must* be in TEST mode when these tests are performed to prevent the Tx generating any RF if keyed by accident. In my list of suspects is relay K1 which switches in the 40m bandpass filter. Although problems rarely occur with the type of contacts used in this relay they do occur, especially if the contact is overstressed during some fault condition. Therefore among the tests I would suggest that you inject a signal via a 1nF or 10nF capacitor at K1's terminal 3 also 4 also 7 also 8, or "scratch" them. Alternatively "scratch" the top ends of L1 and L2 and K1's terminal 7. If all the results of these tests are positive then the cause of the problem is somewhere else in the signal path. Good luck. 73, Geoff GM4ESD Mark Saunders, KJ7BS wrote on Wednesday, September 24, 2008 4:51 AM > Thanks to everyone for the suggestions. Here is some more information > resulting from your suggestions. > > I have no measurable RF output on 40m or any meaningful RX on 40m. > > The RX/TX works on all other bands including 160m. > > I get the same RX/TX results from ANT1 & ANT2 and main. > > I get the same RX results on the receive ANT. Geoffrey Mackenzie-Kennedy wrote on September 23, 2008: > Don and Mark, > > I note that Mark said "virtually no receive on 40m" and not "no > receive on 40m", from which I would understand that his K2 receiver's > sensitivity on 40m has become poor and only strong signals can be > heard. If that is the case then a possible cause of the problem might > be "dirt", for want of a better word, on the contacts of either K1a or > K1b which switch the 40m bandpass filter. During receive any > attenuation of the signal caused by contact resistance here would > reduce the receiver's sensitivity of course, but during transmit the > ALC might compensate for the added loss. > > While I appreciate that the type of contact used in these relays are > not supposed to get dirty, they do once in a very blue moon. K1a acted > up in my K2 which I cured by adding a DC Wet circuit, removed after a > few months. Cycling the relay K1 on and off many times might be worth > trying. > > What I do not understand is why the problem appeared immediately after > the reverse polarity episode, unless the spark was caused by static > that had built up on the antenna and also managed somehow to get to > K1's contacts after passing through the low pass filters, and without > zapping the T-R switch diodes _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by Mark, KJ7BS
If you can hear nothing at all on 40m but the other bands are OK the likely problem is in the low pass filters on the K2 RF board. I surmise relay K2 which selects the 40m filter is not operating. Another possibility is K1 the bandpass filter for 40m though I think that less likely.
U1, the IO controller chip controls the relays. The pin Check pin 27 is correctly controlling relay K2 on the RF board. If the chip is dead this output will stay low. If it goes high on 40m but the relay does not operate, the relay is dead - or the contacts are welded in place. Do the same for pin 25 which controls K1. Mike |
Re: RE: A Bad Thing Happened To My K2 - Update 1
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In reply to this post by Mark, KJ7BS
Mark,
Find out where the problem is before digging into anything, it will greatly simplify your troubleshooting steps. Add a capacitor to your antenna, and use it to inject signals into your K2. Start at the cathode of D6. Here you should hear a signal and noise - keep in mind that there is no filtering of the receiver front end with the antenna connected here, and it will respond to anything your antenna picks up. Next, try the W6 jumper (or pin 3 of J13 if you have the K2 amp keying kit or the K60XV plugged into J13). Here you should hear the 40 meter band because the bandpass filters are now between the antenna and the receiver front end. The level will not be as loud as at the cathode of D6, but should be 'almost as loud'. If you have good 40 meter reception here, move on, but if not, there is something wrong with the 40 meter bandpass filter. Moving on, next try the W1 jumper (or pin 1 of the K160RX option board header). If you still have 40 meter reception here, the T/R switch is good and your problem is in the Low Pass Filter. Once you have isolated the problem area, the remaining troubleshooting steps are greatly simplified. Right now, based on the information we have available, we can only say that the problem lies somewhere in the K2. If you do not find a definitive answer with the steps above, a similar process can be done in transmit using the RF Probe. 73, Don W3FPR Mark Saunders, KJ7BS wrote: > Thanks to everyone for the suggestions. Here is some more information > resulting from your suggestions. > > I have no measurable RF output on 40m or any meaningful RX on 40m. > > The RX/TX works on all other bands including 160m. > > I get the same RX/TX results from ANT1 & ANT2 and main. > > I get the same RX results on the receive ANT. > > Elecraft mailing list Post to: [hidden email] 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: RE: A Bad Thing Happened To My K2 - Update 1
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You might try to read this PDF file that N0SS wrote to find where it is broken.... http://www.n0ss.net/k2_signal_tracing.pdf Lee Buller - K0WA In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine? _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: A Bad Thing Happened To My K2 - Update 10/4/2008
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In reply to this post by Mark, KJ7BS
I removed K12 from the radio and re-wound L25 because one wire broke.
Removing the relay using solder wick was not successful so I used a heat gun to melt the solder on all pads at once. I used aluminum foil to shield the K2 from the heat gun. I cut an opening in the aluminum foil a bit larger than the relay and put it over the PCB exposing only the pads for the relay. I applied only enough heat to see the pads go wet and then used needle-nose pliers to pluck the relay off. I then cleaned up the pads with solder wick which left the holes nice and clean. I've contacted Elecraft for the replacement relay and should have it in a few days. I broke a wire on L25 and had to re-wind it and install it again. I also took the time to install the T/R circuit from Tom N0SS. Now I can use my K2 to drive my AL-811H to a little over 300w with about 10w drive without having to use a foot switch. After replacing K12, my next project on the K2 is to install the KAF2 audio filter board. Then I will have all options except the KPA/100, DSP and 60m modules. I guess at some point I should upgrade S/N 0539 to Revision B. Mark, KJ7BS Glendale, AZ Editor, The SKCC Centurion Elecraft K2 S/N 0539 Fists # 2972 CC 1806 SKCC # 2240 C56 T20 MQFD # 128 QRP-ARCI # 12647 AZ ScQRPions COGRC Emergency Communications -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Mark Saunders, KJ7BS Sent: Monday, September 22, 2008 10:04 PM To: Elecraft Mail List Subject: [Elecraft] A Bad Thing Happened To My K2 Importance: High This evening I had a guest ham in the shack who was curious about my K2 and asked if we could hook it up. So we did. I pointed out which 12v power strip, power cord, and antenna to use. While I was getting the proper computer interface cables hooded up, my guest connected the radio to the power and switched it on. I heard a loud snap and immediately looked in the direction of the K2 operating position. My guest had a strange look on his face and I asked what happened. There was a spark from the outside of the antenna connector on the back of the K2 to the center connector of the coax. That can't happen, right? Wrong. After shutting down the power supply and inspecting things, I discovered my guest had wired the power backwards. Fortunately the reverse polarity circuitry protected the radio and internal battery. The radio was operating from the battery, that's why it came on. I still can't understand where the spark came from. However, I now have virtually NO receive on 40m, that's where the radio was when the spark occurred. I have transmit and receive on all other bands and transmit on 40m, just no receive on 40m. That spark killed something dealing with 40m receive. It is so bad I can't even hear the local oscillator around 7000 KHz with the pre-amp on. There is no CW or SSB receive. Mark, KJ7BS Glendale, AZ Editor, The SKCC Centurion Elecraft K2 S/N 0539 Fists # 2972 CC 1806 SKCC # 2240 C56 T20 MQFD # 128 QRP-ARCI # 12647 AZ ScQRPions COGRC Emergency Communications _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: [hidden email] 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 |
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