K2 frozen at start up
Locked
 
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Hi I'm Silvio IZ5DIY,
while I was running a qrp long-wire setup by a little tuner, I touched my K2 and experienced a "electrostatic" discharge. A storm was coming and a lot of static energy was on air. I had cut - yes had to cut - external wire antenna, I was unable to remove antenna connector from K2 without discharge, or to handle the wire outdoor at the tuner connection. After first discharge experience I switch off K2, but not disconnect... I was to much "spark". Later my cut and try to bring to ground all antenna, next I remove all connection to K2 (no more discharge). I tried to power on again and after Elecraft message the frequency was frozen. No more control or buttons working, only power know was working. I was running qrp on RTTY mode, and it is still locked in this way. I looked at this mailing list archive to see similar experience and I found something. http://elecraft.365791.n2.nabble.com/K2-freeze-at-startup-need-advice-td1099894.html#a1100892 http://elecraft.365791.n2.nabble.com/K2-CONTROL-PANNEL-FREEZE-UP-K7CJA-td3749758.html#a3749758 They lead me to a "fixed tx" behavior. Based on second link thread I check my control board focusing on U6. First I check U6 pin 30 level and it was low: 0,12v. Checked for any problem following DOT-PTT line ( CB - RF - Front): no problem. I check R value at RP4 5-6 and it was around 3K, not 82K as required. I measured level at U6: pin 25 TXD close to 5v (4,94) pin 26 RXD close to 5v pin 27 TX 0v pin 28 RX 0v pin 29 /DASH close to 5v pin 30 /DOT-PTT low 0,12v I measure Q1-Q2 collector: both close to 0v. I think if it is really "stuck on tx" I should find 8T (collector of Q1) at 8v level... but it is low. Measure at Q3-Q4 gate: both to 0v. Next test I made: removing U6 from it socket. I check again resistance at RP4 5-6 and found correct 82K. I check resistance value at different pins at U6 (alone U6) referred to pin 31 VDD U6 pin 29 - 31: high impedance U6 pin 30 - 31: 2,7K My think is U6 is gone. But it's strange it is stuck on TX without 8T level. Any guy can confirm my idea? Any more check? 73, Silvio IZ5DIY ______________________________________________________________ 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 |
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Silvio,
Yes, I would first replace CB U6 and Q3 and Q4, then see how the K2 behaves. With such a strong static discharge, it is difficult to predict what has been damaged, so take it one step at a time until the problems have been resolved. The DOT-PTT signal also goes the the firmware chip on the KSB2 board, so you may find that input has also been damaged. If the "stuck in transmit" condition goes away when the KSB2 option is removed, the KSB2 firmware must be replaced too. With both the TX and RX signals at 0 volts, I would guess that CB Q4 has been damaged, and likely Q3 as well. The firmware thinks the K2 is in transmit because of the fault on the DOT-PTT input, but a Q3 with a gate to source short would prevent the TX output from going to 5 volts. You are likely to have multiple failure points, so take each one a step at a time. 73, Don W3FPR On 10/6/2010 6:05 AM, Silvio IZ5DIY wrote: > Hi I'm Silvio IZ5DIY, > > while I was running a qrp long-wire setup by a little tuner, I touched > my K2 and experienced a "electrostatic" discharge. > A storm was coming and a lot of static energy was on air. I had cut - > yes had to cut - external wire antenna, I was unable to remove antenna > connector from K2 without discharge, or to handle the wire outdoor at > the tuner connection. > > After first discharge experience I switch off K2, but not disconnect... > I was to much "spark". > Later my cut and try to bring to ground all antenna, next I remove all > connection to K2 (no more discharge). > > I tried to power on again and after Elecraft message the frequency was > frozen. No more control or buttons working, only power know was working. > I was running qrp on RTTY mode, and it is still locked in this way. > > I looked at this mailing list archive to see similar experience and I > found something. > http://elecraft.365791.n2.nabble.com/K2-freeze-at-startup-need-advice-td1099894.html#a1100892 > http://elecraft.365791.n2.nabble.com/K2-CONTROL-PANNEL-FREEZE-UP-K7CJA-td3749758.html#a3749758 > > They lead me to a "fixed tx" behavior. > > Based on second link thread I check my control board focusing on U6. > > First I check U6 pin 30 level and it was low: 0,12v. Checked for any > problem following DOT-PTT line ( CB - RF - Front): no problem. > I check R value at RP4 5-6 and it was around 3K, not 82K as required. > > I measured level at U6: > pin 25 TXD close to 5v (4,94) > pin 26 RXD close to 5v > pin 27 TX 0v > pin 28 RX 0v > pin 29 /DASH close to 5v > pin 30 /DOT-PTT low 0,12v > > I measure Q1-Q2 collector: both close to 0v. > I think if it is really "stuck on tx" I should find 8T (collector of Q1) > at 8v level... but it is low. > Measure at Q3-Q4 gate: both to 0v. > > Next test I made: removing U6 from it socket. I check again resistance > at RP4 5-6 and found correct 82K. > I check resistance value at different pins at U6 (alone U6) referred to > pin 31 VDD > U6 pin 29 - 31: high impedance > U6 pin 30 - 31: 2,7K > > My think is U6 is gone. But it's strange it is stuck on TX without 8T level. > > Any guy can confirm my idea? Any more check? > > 73, Silvio IZ5DIY > ______________________________________________________________ > 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 > 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 |
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