Inoperable S-Meter
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I've finished my K2, and everything seems to work just fine except the
S-Meter. I don't think the AGC is working either. My analog skills are somewhat limited, so I'm hoping that someone might advise me. I've copied elecraft support too, but if someone out there has suggestions, I'd appreciate the help. I have a scope and can take measurements. I've verified that the X1 crystal is working. Voltages on U1 look good. Voltages on U2 look low by about 2v. I think I have a signal to D1. Voltages are as follows U2-1 4.1v U2-2 4.1v U2-3 4.1v U2-4 0v U2-6 3.9v U2-7 3.9v U2-8 9.0v Q12-E 8.9v Q12-B 3.8v Q12-C 4.0v Thanks in advance Regards Rich - KE1EV _______________________________________________ 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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Rich,
It would seem your problem extends beyond the S-meter. For starters, I don't like the 9.0 volts that you report on U2-8, that is the voltage rail direct from the 8 volt regulator, so forget about the S-meter for the moment and start by measuring the voltage regulator U4. Once that voltage is within range (8 volts +/- 10%) you can re-check the AGC Threshold setting and see if the S-meter works. The 8R voltage is also quite high, but the regulator may be the root cause of all your problems - fix the regulator problem first. 73, Don W3FPR > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]]On Behalf Of Richard Carter > Sent: Saturday, February 18, 2006 12:03 PM > To: [hidden email]; 'Gary Surrency' > Subject: [Elecraft] Inoperable S-Meter > > > I've finished my K2, and everything seems to work just fine except the > S-Meter. I don't think the AGC is working either. My analog skills are > somewhat limited, so I'm hoping that someone might advise me. I've copied > elecraft support too, but if someone out there has suggestions, I'd > appreciate the help. I have a scope and can take measurements. > > I've verified that the X1 crystal is working. Voltages on U1 look good. > Voltages on U2 look low by about 2v. I think I have a signal to D1. > > Voltages are as follows > > U2-1 4.1v > U2-2 4.1v > U2-3 4.1v > U2-4 0v > U2-6 3.9v > U2-7 3.9v > U2-8 9.0v > Q12-E 8.9v > Q12-B 3.8v > Q12-C 4.0v > > Thanks in advance > Regards > Rich - KE1EV > _______________________________________________ > 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 > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.375 / Virus Database: 267.15.11/264 - Release Date: 2/17/2006 > > _______________________________________________ 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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Don
I thought the numbers looked high, but the regulator is not adjustable. I measured it again and found the 5v regulator high too. The batteries in my voltmeter are low, causing the readings to look high. Here they are again with a fresh battery. U2-1 3.7v U2-2 3.7v U2-3 3.6v U2-4 0v U2-5 3.8V U2-6 3.8v U2-7 3.8v U2-8 8.0v Q12-E 7.8v Q12-B 3.66v Q12-C 3.60v Thanks for your time Rich - KE1EV -----Original Message----- From: Don Wilhelm [mailto:[hidden email]] Sent: Saturday, February 18, 2006 12:27 PM To: [hidden email]; [hidden email] Subject: RE: [Elecraft] Inoperable S-Meter Rich, It would seem your problem extends beyond the S-meter. For starters, I don't like the 9.0 volts that you report on U2-8, that is the voltage rail direct from the 8 volt regulator, so forget about the S-meter for the moment and start by measuring the voltage regulator U4. Once that voltage is within range (8 volts +/- 10%) you can re-check the AGC Threshold setting and see if the S-meter works. The 8R voltage is also quite high, but the regulator may be the root cause of all your problems - fix the regulator problem first. 73, Don W3FPR > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]]On Behalf Of Richard Carter > Sent: Saturday, February 18, 2006 12:03 PM > To: [hidden email]; 'Gary Surrency' > Subject: [Elecraft] Inoperable S-Meter > > > I've finished my K2, and everything seems to work just fine except the > S-Meter. I don't think the AGC is working either. My analog skills are > somewhat limited, so I'm hoping that someone might advise me. I've > copied elecraft support too, but if someone out there has suggestions, > I'd appreciate the help. I have a scope and can take measurements. > > I've verified that the X1 crystal is working. Voltages on U1 look good. > Voltages on U2 look low by about 2v. I think I have a signal to D1. > > Voltages are as follows > > U2-1 4.1v > U2-2 4.1v > U2-3 4.1v > U2-4 0v > U2-6 3.9v > U2-7 3.9v > U2-8 9.0v > Q12-E 8.9v > Q12-B 3.8v > Q12-C 4.0v > > Thanks in advance > Regards > Rich - KE1EV > _______________________________________________ > 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 > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.375 / Virus Database: 267.15.11/264 - Release Date: > 2/17/2006 > > _______________________________________________ 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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Rich,
Yes, those numbers look a lot more sensible, and furthermore, those DC readings seem to be close to normal. I suggest you get out your 'scope while driving the K2 with a healthy sized input signal and see if you can find any IF energy at the input of the control board U1 mixer - that should in turn produce an output signal at the output of the AGC mixer at about 155 kHz. That 155 kHz signal should pass through U2 from pin 6 to pin 7 and the AC signal should be rectified by diode D1, adding to the DC bias from the voltage at U2 pin 5 and modifying the DC level at the base of Q12 with the signal strength - stronger signals will increase the Q12 base voltage and weaker signals will allow it to drift toward the setting supplied by the DC Biasing controlled by the AGC Threshold pot setting. I don't know the capabilities of your 'scope, so I don't know how low a signal level you can measure. There is a chance that you do not have a good path between the IF takeoff point (IF OUT) after the varaible filter and the input to Control Board U1 pin 1. If your 'scope can measure small signals, it would be informative to see if the signal is getting to the AGC mixer input. Even if you cannot observe the actual signals at U1 with your 'scope, you should see the voltage at the base of Q12 increase with a steady strong signal applied to the K2 input. Once you have verified that the AGC is responding to changes in signal strength, we can look at the S-meter problem if it still is present. 73, Don W3FPR > -----Original Message----- > > Don > I thought the numbers looked high, but the regulator is not adjustable. I > measured it again and found the 5v regulator high too. The > batteries in my > voltmeter are low, causing the readings to look high. Here they are again > with a fresh battery. > > U2-1 3.7v > U2-2 3.7v > U2-3 3.6v > U2-4 0v > U2-5 3.8V > U2-6 3.8v > U2-7 3.8v > U2-8 8.0v > Q12-E 7.8v > Q12-B 3.66v > Q12-C 3.60v > > Thanks for your time > Rich - KE1EV > > > -----Original Message----- > > Rich, > > It would seem your problem extends beyond the S-meter. For starters, I > don't like the 9.0 volts that you report on U2-8, that is the voltage rail > direct from the 8 volt regulator, so forget about the S-meter for > the moment > and start by measuring the voltage regulator U4. Once that voltage is > within range (8 volts +/- 10%) you can re-check the AGC Threshold setting > and see if the S-meter works. > > The 8R voltage is also quite high, but the regulator may be the root cause > of all your problems - fix the regulator problem first. > > 73, > Don W3FPR > _______________________________________________ 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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Thanks Don. It's a good scope, better than my skills. I'll give it a try.
I'll let you know what I find. Regards Rich -----Original Message----- From: Don Wilhelm [mailto:[hidden email]] Sent: Saturday, February 18, 2006 8:40 PM To: [hidden email] Cc: [hidden email] Subject: RE: [Elecraft] Inoperable S-Meter Rich, Yes, those numbers look a lot more sensible, and furthermore, those DC readings seem to be close to normal. I suggest you get out your 'scope while driving the K2 with a healthy sized input signal and see if you can find any IF energy at the input of the control board U1 mixer - that should in turn produce an output signal at the output of the AGC mixer at about 155 kHz. That 155 kHz signal should pass through U2 from pin 6 to pin 7 and the AC signal should be rectified by diode D1, adding to the DC bias from the voltage at U2 pin 5 and modifying the DC level at the base of Q12 with the signal strength - stronger signals will increase the Q12 base voltage and weaker signals will allow it to drift toward the setting supplied by the DC Biasing controlled by the AGC Threshold pot setting. I don't know the capabilities of your 'scope, so I don't know how low a signal level you can measure. There is a chance that you do not have a good path between the IF takeoff point (IF OUT) after the varaible filter and the input to Control Board U1 pin 1. If your 'scope can measure small signals, it would be informative to see if the signal is getting to the AGC mixer input. Even if you cannot observe the actual signals at U1 with your 'scope, you should see the voltage at the base of Q12 increase with a steady strong signal applied to the K2 input. Once you have verified that the AGC is responding to changes in signal strength, we can look at the S-meter problem if it still is present. 73, Don W3FPR > -----Original Message----- > > Don > I thought the numbers looked high, but the regulator is not > adjustable. I measured it again and found the 5v regulator high too. Snip... _______________________________________________ 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 Don Wilhelm-3
Rich (reading over Don's shoulder here)...
Does your S-meter move from min to max as you run the RF gain up and down? That would help pin down the issue to either the I.F (in the K2 that's called "RF" gain) gain control voltage or the AGC system itself. The RF Gain pot does adjusts the same voltage manually that the AGC system is supposed to control automatically. Ron AC7AC -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Don Wilhelm Sent: Saturday, February 18, 2006 5:40 PM To: [hidden email] Cc: [hidden email] Subject: RE: [Elecraft] Inoperable S-Meter Rich, Yes, those numbers look a lot more sensible, and furthermore, those DC readings seem to be close to normal. I suggest you get out your 'scope while driving the K2 with a healthy sized input signal and see if you can find any IF energy at the input of the control board U1 mixer - that should in turn produce an output signal at the output of the AGC mixer at about 155 kHz. That 155 kHz signal should pass through U2 from pin 6 to pin 7 and the AC signal should be rectified by diode D1, adding to the DC bias from the voltage at U2 pin 5 and modifying the DC level at the base of Q12 with the signal strength - stronger signals will increase the Q12 base voltage and weaker signals will allow it to drift toward the setting supplied by the DC Biasing controlled by the AGC Threshold pot setting. I don't know the capabilities of your 'scope, so I don't know how low a signal level you can measure. There is a chance that you do not have a good path between the IF takeoff point (IF OUT) after the varaible filter and the input to Control Board U1 pin 1. If your 'scope can measure small signals, it would be informative to see if the signal is getting to the AGC mixer input. Even if you cannot observe the actual signals at U1 with your 'scope, you should see the voltage at the base of Q12 increase with a steady strong signal applied to the K2 input. Once you have verified that the AGC is responding to changes in signal strength, we can look at the S-meter problem if it still is present. 73, Don W3FPR > -----Original Message----- > > Don > I thought the numbers looked high, but the regulator is not > adjustable. I measured it again and found the 5v regulator high too. > The batteries in my voltmeter are low, causing the readings to look > high. Here they are again with a fresh battery. > > U2-1 3.7v > U2-2 3.7v > U2-3 3.6v > U2-4 0v > U2-5 3.8V > U2-6 3.8v > U2-7 3.8v > U2-8 8.0v > Q12-E 7.8v > Q12-B 3.66v > Q12-C 3.60v > > Thanks for your time > Rich - KE1EV > > > -----Original Message----- > > Rich, > > It would seem your problem extends beyond the S-meter. For starters, > I don't like the 9.0 volts that you report on U2-8, that is the > voltage rail direct from the 8 volt regulator, so forget about the > S-meter for the moment and start by measuring the voltage regulator > U4. Once that voltage is within range (8 volts +/- 10%) you can > re-check the AGC Threshold setting and see if the S-meter works. > > The 8R voltage is also quite high, but the regulator may be the root > cause of all your problems - fix the regulator problem first. > > 73, > Don W3FPR > _______________________________________________ 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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