K2 PA
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I just replaced the PA's on my K2. I replaced Q7, Q8, Q11, Q13 with parts
from the Elecraft PA Replacement Kit. I have done this in the past with no problems. Power is supplied from a switching power supply that supplies power to a power distribution box that has a fuse for each output. This distribution box supplies power to a small 2 meter 70cm mobile/base radio and a LED light strip. This setup has been working with no trouble for a while. Now as soon as I plug in the power cord to the K2 all of the power coming from the distribution box shuts off. I used the same power cord on two other radios and it worked just fine. So the problem lies in the K2. While working on the K2 I messed with replacing only the parts mentioned above. I went over the PA's with a magnifying glass looking for solder bridges and other faults and could not find any. This problem did not exist before I changed the PA's. I would appreciate any ideas as to what may be the problem. Aaron K5ATG ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Hi,
Did you do the resistance check on page 76 of the latest manual. It checks for a short from the collector of Q7 or Q8 to ground after installing the heat sink. If there is a short there, the manual suggests the most likely cause. Lou W2ROW -- Sent from: http://elecraft.365791.n2.nabble.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Aaron,
Are you stating that with the K2 power switch in the OFF position and simply plugging the power cord into the rear power jack, causes the supply to shut down? 73, Dave, W8FGU On April 28, 2020 18:16:47 Lou Voerman W2ROW <[hidden email]> wrote: > Hi, > > Did you do the resistance check on page 76 of the latest manual. It checks > for a short from the collector of Q7 or Q8 to ground after installing the > heat sink. If there is a short there, the manual suggests the most likely > cause. > > Lou W2ROW > > > > -- > Sent from: http://elecraft.365791.n2.nabble.com/ > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Aaron K5ATG
Aaron,
Did you replace the PA transistor thermal pads? And if so, did you smooth out and metal projections on the heat sink before installing the heatsink? Those are necessary steps to prevent a short from the PA transistor tabs (also the collector) to the heatsink. You must always do a resistance check from the Q7 and/or Q8 collector leads to ground after installing the heatsink. If that check shows you a zero or very low resistance, then you need to investigate the cause - usually metal embedded in the thermal pads, or jagged edges on the heatsink where the heatsink contacts the thermal pads. 73, Don W3FPR On 4/28/2020 4:22 PM, Aaron K5ATG wrote: > I just replaced the PA's on my K2. I replaced Q7, Q8, Q11, Q13 with parts > from the Elecraft PA Replacement Kit. I have done this in the past with no > problems. Power is supplied from a switching power supply that supplies > power to a power distribution box that has a fuse for each output. This > distribution box supplies power to a small 2 meter 70cm mobile/base radio > and a LED light strip. This setup has been working with no trouble for a > while. Now as soon as I plug in the power cord to the K2 all of the power > coming from the distribution box shuts off. I used the same power cord on > two other radios and it worked just fine. So the problem lies in the K2. > While working on the K2 I messed with replacing only the parts mentioned > above. I went over the PA's with a magnifying glass looking for solder > bridges and other faults and could not find any. This problem did not exist > before I changed the PA's. I would appreciate any ideas as to what may be > the problem. > Aaron K5ATG > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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