RE: [Elecraft] K2 dead xmtr
Larry, With those RF voltage measurements, I would say that the final output transistors have likely failed - that goes along with your earlier report that the power out decreased rapidly to zip. There is only one other possibility that I can think of, and that would be the transmit signal being shorted somewhere - so before blaming the finals themselves, check that Q2 is operating properly - the juction of D3 and D4 in the TR switch should be at a low voltage during receive and go up somewhere close to 8 volts during transmit. If the receiver is still functioning properly, a short in the Low Pass Filter is quite unlikly because that kind of fault would drag the receiver way down too. 73, Don W3FPR -Original Message- From: Larry Phipps [mailto:[EMAIL PROTECTED] Sent: Sunday, December 11, 2005 10:46 PM To: [EMAIL PROTECTED] Cc: Elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 dead xmtr Hi Don. The levels are high everywhere in the chain up through the bases of Q7-8. Requested power is immaterial in this case, since the ALC sees zero detected power, and therefore is pegged at 5v all the time. I measured the levels with a scope, and divided the p-p values by 2.82 to compare with the voltage probe reference levels in the manual. BTW, I removed the KAT2 and KSB2 to simplify access and minimize the number of possible fault zones. W6 - .28 Vrms Q5 case- 1.4 Vrms Q6 tab- 3.5 Vrms Q7,8 base- 1.4 Vrms RF out- .55 Vrms Note: These waveforms are pretty dirty looking except on 10m, where I made these measurements. Larry N8LP Don Wilhelm wrote: Larry, With the requested power set at 5 watts, send us the RF Voltage levels at the W6 jumper, Q5 collector (case), Q6 collector (tab), Q7,Q8 base, and the RF Output jack. With that info, we should be able to home in on the problem area. 73, Don W3FPR -Original Message- OK. I'm hoping someone has seen this before I start tearing into things (and tearing my hair out). My K2 started to lose power yesterday. Within an hour, the output dropped to close to zero (1mW on 160m, 40mW on 10m). There are no signs of distress or burning odors. I checked the ALC... pinned at 5v. Everything looks good in terms of levels/frequencies thru the XMIT mixer and filters, except the rf levels are higher than indicated in the manual. I suspect this is due to the ALC being wide open. The dc levels for Q5, Q6, and Q7-8 bases are normal, and the resistance checks on Q7-8 are OK. 8T looks fine. But the rf levels are all considerably high, and look pretty ratty except on 10m. The rig draws about 600ma in xmit. Anyone seen this before? Larry N8LP -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.371 / Virus Database: 267.13.13/198 - Release Date: 12/12/2005 ___ 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] K2 dead xmtr
I think I checked the T/R switch already, but I'll double-check. The thing that's weird is that the DC voltages and resistance checks on the finals are OK. I never got a Hi-Cur warning at any time before the failure (or since). The rig draws about 600ma during xmit. Thanks for the feedback. Larry N8LP Don Wilhelm wrote: Larry, With those RF voltage measurements, I would say that the final output transistors have likely failed - that goes along with your earlier report that the power out decreased rapidly to zip. There is only one other possibility that I can think of, and that would be the transmit signal being shorted somewhere - so before blaming the finals themselves, check that Q2 is operating properly - the juction of D3 and D4 in the TR switch should be at a low voltage during receive and go up somewhere close to 8 volts during transmit. If the receiver is still functioning properly, a short in the Low Pass Filter is quite unlikly because that kind of fault would drag the receiver way down too. 73, Don W3FPR -Original Message- From: Larry Phipps [mailto:[EMAIL PROTECTED] Sent: Sunday, December 11, 2005 10:46 PM To: [EMAIL PROTECTED] Cc: Elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 dead xmtr Hi Don. The levels are high everywhere in the chain up through the bases of Q7-8. Requested power is immaterial in this case, since the ALC sees zero detected power, and therefore is pegged at 5v all the time. I measured the levels with a scope, and divided the p-p values by 2.82 to compare with the voltage probe reference levels in the manual. BTW, I removed the KAT2 and KSB2 to simplify access and minimize the number of possible fault zones. W6 - .28 Vrms Q5 case- 1.4 Vrms Q6 tab- 3.5 Vrms Q7,8 base- 1.4 Vrms RF out- .55 Vrms Note: These waveforms are pretty dirty looking except on 10m, where I made these measurements. Larry N8LP Don Wilhelm wrote: Larry, With the requested power set at 5 watts, send us the RF Voltage levels at the W6 jumper, Q5 collector (case), Q6 collector (tab), Q7,Q8 base, and the RF Output jack. With that info, we should be able to home in on the problem area. 73, Don W3FPR -Original Message- OK. I'm hoping someone has seen this before I start tearing into things (and tearing my hair out). My K2 started to lose power yesterday. Within an hour, the output dropped to close to zero (1mW on 160m, 40mW on 10m). There are no signs of distress or burning odors. I checked the ALC... pinned at 5v. Everything looks good in terms of levels/frequencies thru the XMIT mixer and filters, except the rf levels are higher than indicated in the manual. I suspect this is due to the ALC being wide open. The dc levels for Q5, Q6, and Q7-8 bases are normal, and the resistance checks on Q7-8 are OK. 8T looks fine. But the rf levels are all considerably high, and look pretty ratty except on 10m. The rig draws about 600ma in xmit. Anyone seen this before? Larry N8LP -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.371 / Virus Database: 267.13.13/198 - Release Date: 12/12/2005 ___ 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] K2 dead xmtr
Larry; I suggest you call Elecraft customer support on this. Something tells me they will want you to check out the KSB2 module to find the problem. Good luck! On Dec 12, 2005, at 7:52 AM, Larry Phipps wrote: I think I checked the T/R switch already, but I'll double-check. The thing that's weird is that the DC voltages and resistance checks on the finals are OK. I never got a Hi-Cur warning at any time before the failure (or since). The rig draws about 600ma during xmit. Thanks for the feedback. Larry N8LP Don Wilhelm wrote: Larry, With those RF voltage measurements, I would say that the final output transistors have likely failed - that goes along with your earlier report that the power out decreased rapidly to zip. There is only one other possibility that I can think of, and that would be the transmit signal being shorted somewhere - so before blaming the finals themselves, check that Q2 is operating properly - the juction of D3 and D4 in the TR switch should be at a low voltage during receive and go up somewhere close to 8 volts during transmit. If the receiver is still functioning properly, a short in the Low Pass Filter is quite unlikly because that kind of fault would drag the receiver way down too. 73, Don W3FPR -Original Message- From: Larry Phipps [mailto:[EMAIL PROTECTED] Sent: Sunday, December 11, 2005 10:46 PM To: [EMAIL PROTECTED] Cc: Elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 dead xmtr Hi Don. The levels are high everywhere in the chain up through the bases of Q7-8. Requested power is immaterial in this case, since the ALC sees zero detected power, and therefore is pegged at 5v all the time. I measured the levels with a scope, and divided the p-p values by 2.82 to compare with the voltage probe reference levels in the manual. BTW, I removed the KAT2 and KSB2 to simplify access and minimize the number of possible fault zones. W6 - .28 Vrms Q5 case- 1.4 Vrms Q6 tab- 3.5 Vrms Q7,8 base- 1.4 Vrms RF out- .55 Vrms Note: These waveforms are pretty dirty looking except on 10m, where I made these measurements. Larry N8LP Don Wilhelm wrote: Larry, With the requested power set at 5 watts, send us the RF Voltage levels at the W6 jumper, Q5 collector (case), Q6 collector (tab), Q7,Q8 base, and the RF Output jack. With that info, we should be able to home in on the problem area. 73, Don W3FPR -Original Message- OK. I'm hoping someone has seen this before I start tearing into things (and tearing my hair out). My K2 started to lose power yesterday. Within an hour, the output dropped to close to zero (1mW on 160m, 40mW on 10m). There are no signs of distress or burning odors. I checked the ALC... pinned at 5v. Everything looks good in terms of levels/frequencies thru the XMIT mixer and filters, except the rf levels are higher than indicated in the manual. I suspect this is due to the ALC being wide open. The dc levels for Q5, Q6, and Q7-8 bases are normal, and the resistance checks on Q7-8 are OK. 8T looks fine. But the rf levels are all considerably high, and look pretty ratty except on 10m. The rig draws about 600ma in xmit. Anyone seen this before? Larry N8LP -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.371 / Virus Database: 267.13.13/198 - Release Date: 12/12/2005 ___ 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 -Jack Brindle, W6FB === ___ 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] K2 dead xmtr
Thanks Jack, I'll call them, but I removed the KSB2 module and I still have the problem. There appears to be plenty of drive either way. I ordered a PA replacement kit just to have it on hand. I can get the xstrs locally, but not all the mounting stuff. Larry N8LP Jack Brindle wrote: Larry; I suggest you call Elecraft customer support on this. Something tells me they will want you to check out the KSB2 module to find the problem. Good luck! On Dec 12, 2005, at 7:52 AM, Larry Phipps wrote: I think I checked the T/R switch already, but I'll double-check. The thing that's weird is that the DC voltages and resistance checks on the finals are OK. I never got a Hi-Cur warning at any time before the failure (or since). The rig draws about 600ma during xmit. Thanks for the feedback. Larry N8LP Don Wilhelm wrote: Larry, With those RF voltage measurements, I would say that the final output transistors have likely failed - that goes along with your earlier report that the power out decreased rapidly to zip. There is only one other possibility that I can think of, and that would be the transmit signal being shorted somewhere - so before blaming the finals themselves, check that Q2 is operating properly - the juction of D3 and D4 in the TR switch should be at a low voltage during receive and go up somewhere close to 8 volts during transmit. If the receiver is still functioning properly, a short in the Low Pass Filter is quite unlikly because that kind of fault would drag the receiver way down too. 73, Don W3FPR -Original Message- From: Larry Phipps [mailto:[EMAIL PROTECTED] Sent: Sunday, December 11, 2005 10:46 PM To: [EMAIL PROTECTED] Cc: Elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 dead xmtr Hi Don. The levels are high everywhere in the chain up through the bases of Q7-8. Requested power is immaterial in this case, since the ALC sees zero detected power, and therefore is pegged at 5v all the time. I measured the levels with a scope, and divided the p-p values by 2.82 to compare with the voltage probe reference levels in the manual. BTW, I removed the KAT2 and KSB2 to simplify access and minimize the number of possible fault zones. W6 - .28 Vrms Q5 case- 1.4 Vrms Q6 tab- 3.5 Vrms Q7,8 base- 1.4 Vrms RF out- .55 Vrms Note: These waveforms are pretty dirty looking except on 10m, where I made these measurements. Larry N8LP Don Wilhelm wrote: Larry, With the requested power set at 5 watts, send us the RF Voltage levels at the W6 jumper, Q5 collector (case), Q6 collector (tab), Q7,Q8 base, and the RF Output jack. With that info, we should be able to home in on the problem area. 73, Don W3FPR -Original Message- OK. I'm hoping someone has seen this before I start tearing into things (and tearing my hair out). My K2 started to lose power yesterday. Within an hour, the output dropped to close to zero (1mW on 160m, 40mW on 10m). There are no signs of distress or burning odors. I checked the ALC... pinned at 5v. Everything looks good in terms of levels/frequencies thru the XMIT mixer and filters, except the rf levels are higher than indicated in the manual. I suspect this is due to the ALC being wide open. The dc levels for Q5, Q6, and Q7-8 bases are normal, and the resistance checks on Q7-8 are OK. 8T looks fine. But the rf levels are all considerably high, and look pretty ratty except on 10m. The rig draws about 600ma in xmit. Anyone seen this before? Larry N8LP -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.371 / Virus Database: 267.13.13/198 - Release Date: 12/12/2005 ___ 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 -Jack Brindle, W6FB === ___ 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] K2 dead xmtr
Larry, Exactly where are the RF levels higher than normal? Obviously not at the output of the Low Pass filter or you would have power output (unless you have the tuner and have set it to ANT2 instead of ANT1 or something like that). With the requested power set at 5 watts, send us the RF Voltage levels at the W6 jumper, Q5 collector (case), Q6 collector (tab), Q7,Q8 base, and the RF Output jack. With that info, we should be able to home in on the problem area. 73, Don W3FPR -Original Message- OK. I'm hoping someone has seen this before I start tearing into things (and tearing my hair out). My K2 started to lose power yesterday. Within an hour, the output dropped to close to zero (1mW on 160m, 40mW on 10m). There are no signs of distress or burning odors. I checked the ALC... pinned at 5v. Everything looks good in terms of levels/frequencies thru the XMIT mixer and filters, except the rf levels are higher than indicated in the manual. I suspect this is due to the ALC being wide open. The dc levels for Q5, Q6, and Q7-8 bases are normal, and the resistance checks on Q7-8 are OK. 8T looks fine. But the rf levels are all considerably high, and look pretty ratty except on 10m. The rig draws about 600ma in xmit. Anyone seen this before? Larry N8LP ___ 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] K2 dead xmtr
Hi Don. The levels are high everywhere in the chain up through the bases of Q7-8. Requested power is immaterial in this case, since the ALC sees zero detected power, and therefore is pegged at 5v all the time. I measured the levels with a scope, and divided the p-p values by 2.82 to compare with the voltage probe reference levels in the manual. BTW, I removed the KAT2 and KSB2 to simplify access and minimize the number of possible fault zones. W6 - .28 Vrms Q5 case- 1.4 Vrms Q6 tab- 3.5 Vrms Q7,8 base- 1.4 Vrms RF out- .55 Vrms Note: These waveforms are pretty dirty looking except on 10m, where I made these measurements. Larry N8LP Don Wilhelm wrote: Larry, With the requested power set at 5 watts, send us the RF Voltage levels at the W6 jumper, Q5 collector (case), Q6 collector (tab), Q7,Q8 base, and the RF Output jack. With that info, we should be able to home in on the problem area. 73, Don W3FPR -Original Message- OK. I'm hoping someone has seen this before I start tearing into things (and tearing my hair out). My K2 started to lose power yesterday. Within an hour, the output dropped to close to zero (1mW on 160m, 40mW on 10m). There are no signs of distress or burning odors. I checked the ALC... pinned at 5v. Everything looks good in terms of levels/frequencies thru the XMIT mixer and filters, except the rf levels are higher than indicated in the manual. I suspect this is due to the ALC being wide open. The dc levels for Q5, Q6, and Q7-8 bases are normal, and the resistance checks on Q7-8 are OK. 8T looks fine. But the rf levels are all considerably high, and look pretty ratty except on 10m. The rig draws about 600ma in xmit. Anyone seen this before? Larry N8LP ___ 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
