[Elecraft] K2: AGC Problem
With my new K2 i have a strange AGC behavior. I cannot detect a difference between AGC on and off. The voltage at pin 5 U2 is exactly 3.8v after changing the 8V regulator to a better one. All my earlier k2's had a large increase in AF when switching off AGC. I possibly made a short between pin 5 and pin 6 of u2 when measuríng the AGC voltage at pin 5. So possibly 3.8 V came to pin 6. Do i have a defective u2? Reception works very well, only swiching on/off of the AGC is without any change. Some hints for me? Michael, DC0ZO K3 #1999, K2 #6614 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] K2: AGC Problem
Michael, Is this new K2 as sensitive (ability to receive weak signals) as the prior ones? If not, you have have a fault somewhere in the receiver section. Do strong signals activate the S-meter bargraph? Try adjusting the S-meter (CAL S-LO and CAL S-HI) as indicated in the manual, then if you have an XG1 or XG2 or other source of a 50 uV signal, connect that to the antenna and see how close that signal source comes to indicating S-9 on 40 meters with the preamp off. If it indicates anywhere between S-7 and S-9, there is nothing wrong with the receiver, and you can adjust for an S-9 indication using CAL S HI. If the receiver is functioning well according to the above checks, then it may be that the AGC OFF signal is not doing it proper function. Check the orientation of Control Board D2. Then, if properly oriented, be certain the voltage at the cathode goes to a low value when the AGC is turned off - if it does not, check pin 9 of CB U6 - it should be the same voltage as the D2 cathode - and if that pin does not go low when AGC is off, the microprocessor chip has a bed output pin (pin 9). 73, Don W3FPR Michael van Hauten wrote: With my new K2 i have a strange AGC behavior. I cannot detect a difference between AGC on and off. The voltage at pin 5 U2 is exactly 3.8v after changing the 8V regulator to a better one. All my earlier k2's had a large increase in AF when switching off AGC. I possibly made a short between pin 5 and pin 6 of u2 when measuríng the AGC voltage at pin 5. So possibly 3.8 V came to pin 6. Do i have a defective u2? Reception works very well, only swiching on/off of the AGC is without any change. Some hints for me? Michael, DC0ZO K3 #1999, K2 #6614 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
RE: [Elecraft] K2 AGC problem
Sjoerd, Your AGC symptoms sound similar to some of what I found wrong with s/n 3641 when I bought it used. You can find a lot of details in the elecraft archive - (search for low audio on K2 s/n 3641). Among other problems, I had a leaky C10 cap in the AGC circuit, upsetting the AGC control circuit /AGCOFF. You might want to check there, to make sure there is no signal on pin U1-2. 73 de chris K6DBG ___ 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
[Elecraft] K2 AGC Problem
Sjoerd, When measuring millivolts some voltmeters are not very accurate. I've seen them err as much as 40-50 percent. Compare two or three meters and see the results. Also, some crystals don't put out a pure sine wave making RMS measurements less acccurate. Look at it on an o'scope if one is available and calculate the RMS from the waveform on the screen. When working with millivolts there are a lot of factors that can affect accuracy that are less of a problem when measuring higher voltages. Just some observations. Hope you get it working soon to your satisfaction. Jim, AB0UK K2/100 S/N 4787 - Crystal filter output seems quite low, it reads 0,17 Vrms, instead of the given 0,35V .. tried this with different BFO settings, no significant difference. The input of the filter is about 2,15 Vrms with a jumper over the NB connector (5 dB more than normal) ___ 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 AGC Problem
Jim, AB0UK wrote: When measuring millivolts some voltmeters are not very accurate. I've seen them err as much as 40-50 percent. Compare two or three meters and see the results. Also, some crystals don't put out a pure sine wave making RMS measurements less acccurate. Look at it on an o'scope if one is available and calculate the RMS from the waveform on the screen. When working with millivolts there are a lot of factors that can affect accuracy that are less of a problem when measuring higher voltages. Just some observations. Hope you get it working soon to your satisfaction. \-- You make an excellent point Jim. One simply cannot measure an RF signal with a DMM with any accuracy. Even with an RF Probe accuracy at low levels will vary widely because most RF probes use a diode rectifier to provide a DC voltage for the meter to indicate. Diodes become very non-linear at low levels. The best instrument for such measurements is a suitable oscilloscope with an 10:1 isolating probe designed for the frequencies involved. Ron AC7AC ___ 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 AGC problem
Hello all, Just some added info abt my K2's problem. Measured Vagc at pin 5 of the IF amp: -No antenna connected AGC on: 3.83V -no antenna connected AGC off: 3.82V -40m antenna connected: 3.90V (my FT-1000D shows abt S5 noise) -XG2 connected :3.99V (50uV level, should be S9) Found a post from N6IZ in 2004 that stated that Vagc varies about 100mV per 10dB. ( http://ac6rm.net/mailarchive/html/elecraft-list/2004-10/msg00085.html ) In my case that says my S9 level is only about 16 dB above noise level... Is there anyone who measured Valc at some point and can tell me if these values are way off? Thanks again, Sjoerd PE2SVN -Oorspronkelijk bericht- Van: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Namens Sjoerd Verzonden: dinsdag 29 augustus 2006 22:56 Aan: elecraft@mailman.qth.net Onderwerp: [Elecraft] K2 AGC problem Hello all, While operating my K2 and switching between bands a lot i noticed my AGC is a bit strange. When trying to set the AGC treshold following Don FPR's instructions i find that the noise level is not changing with the AGC treshold pot with both preamp on and off. There is a difference in noise level between preamp on or off but there not enough noise to trigger the AGC, even with preamp on. Could this be a lack of gain in the receiver or is the ALC circuit wrong? S-meter seems OK to me and the S-meter readings do change with the ALC treshold. Hope to get this nice toy even better.. 73, Sjoerd, PE2SVN ___ 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 ___ 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 AGC problem
Sjoerd, If you look at the MC1350 data sheet, you will find the AGC characteristics for operation wiht a 12 volt supply to the chip and that graph indicates that the gain changes almost linearly from 0 dB to 20dB with an AGC voltage change from 5 to 6 volts, or 10 dB for a 500 mV change, and the rate of change increases abruptly above the 6 volt level. However, the K2 uses that IF amplifier chip at an 8 volt supply, so as a rough guess, the voltages should be multiplied by a factor of 2/3. I have not attempted to characterize this amplifier at an 8 volt supply. Fact 2 - the gain of the IF Amp is governed by the current rather than the voltage into the AGC pin, so you should conclude that there are several dependencies that will modify the actual voltage required for a given gain. I would suggest that you set the AGC Threshold somewhere between 3.7 and 3.8 volts as measured at Control Board U2 pin 5. You may end up with some slight reduction of gain between AGC on and AGC off, but lower voltage here will tend to produce problems with CAL S HI and CAL S LO settings. If you are willing to live with the consequences of using a voltage lower than 3.7 volts to produce less change between AGC ON/OFF, then you must accept the fact that you will have a weaker AGC gain reduction overall, and your S-meter may produce readings that are different from the norm. You may not have any problem at all, only a consequence of the AGC action produced by your high noise level. 73, Don W3FPR -Original Message- Hello all, Just some added info abt my K2's problem. Measured Vagc at pin 5 of the IF amp: -No antenna connected AGC on: 3.83V -no antenna connected AGC off:3.82V -40m antenna connected: 3.90V (my FT-1000D shows abt S5 noise) -XG2 connected : 3.99V (50uV level, should be S9) Found a post from N6IZ in 2004 that stated that Vagc varies about 100mV per 10dB. ( http://ac6rm.net/mailarchive/html/elecraft-list/2004-10/msg00085.html ) In my case that says my S9 level is only about 16 dB above noise level... Is there anyone who measured Valc at some point and can tell me if these values are way off? Thanks again, Sjoerd PE2SVN ___ 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 AGC problem
Don, Ok about the MC1350 specs, and my noise level is very high, but i am afraid that with less noise there is a problem. I did some more measurements end followed the signal tracing procedure, where i find 2 questionable things: - Crystal filter output seems quite low, it reads 0,17 Vrms, instead of the given 0,35V .. tried this with different BFO settings, no significant difference. The input of the filter is about 2,15 Vrms with a jumper over the NB connector (5 dB more than normal) - AGC @ saturation seems way too low, it reads about 4,3 volts where it should be 6,9V. My opinion is that there is some sort of fault in the AGC circuit, that causes no difference in noise level with AGC on or off, and also a big difference in audio level between a S3 and a S9+ station. I have changed C8 a while ago to stop the receive from muting with AGC off, Is it possible that the ACG oscillator level is too low because of this? The receive seems to hear well, compared to my FT-1000. Just the big difference in audio levels worries me.. Thanks again, Sjoerd PE2SVN -Oorspronkelijk bericht- Van: Don Wilhelm [mailto:[EMAIL PROTECTED] Verzonden: woensdag 30 augustus 2006 14:02 Aan: Sjoerd; elecraft@mailman.qth.net Onderwerp: RE: [Elecraft] K2 AGC problem Sjoerd, If you look at the MC1350 data sheet, you will find the AGC characteristics for operation wiht a 12 volt supply to the chip and that graph indicates that the gain changes almost linearly from 0 dB to 20dB with an AGC voltage change from 5 to 6 volts, or 10 dB for a 500 mV change, and the rate of change increases abruptly above the 6 volt level. However, the K2 uses that IF amplifier chip at an 8 volt supply, so as a rough guess, the voltages should be multiplied by a factor of 2/3. I have not attempted to characterize this amplifier at an 8 volt supply. Fact 2 - the gain of the IF Amp is governed by the current rather than the voltage into the AGC pin, so you should conclude that there are several dependencies that will modify the actual voltage required for a given gain. I would suggest that you set the AGC Threshold somewhere between 3.7 and 3.8 volts as measured at Control Board U2 pin 5. You may end up with some slight reduction of gain between AGC on and AGC off, but lower voltage here will tend to produce problems with CAL S HI and CAL S LO settings. If you are willing to live with the consequences of using a voltage lower than 3.7 volts to produce less change between AGC ON/OFF, then you must accept the fact that you will have a weaker AGC gain reduction overall, and your S-meter may produce readings that are different from the norm. You may not have any problem at all, only a consequence of the AGC action produced by your high noise level. 73, Don W3FPR -Original Message- Hello all, Just some added info abt my K2's problem. Measured Vagc at pin 5 of the IF amp: -No antenna connected AGC on: 3.83V -no antenna connected AGC off:3.82V -40m antenna connected: 3.90V (my FT-1000D shows abt S5 noise) -XG2 connected : 3.99V (50uV level, should be S9) Found a post from N6IZ in 2004 that stated that Vagc varies about 100mV per 10dB. ( http://ac6rm.net/mailarchive/html/elecraft-list/2004-10/msg00085.html ) In my case that says my S9 level is only about 16 dB above noise level... Is there anyone who measured Valc at some point and can tell me if these values are way off? Thanks again, Sjoerd PE2SVN ___ 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 AGC problem
Sjoerd, Your first point about the low output from the crystal filter with an input that is normal would indicate that either you have a crystal problem or the filter is not properly matched. Check T7 to see if it has the proper turns ratio (20:5), and the 5 turn winding goes toward the crystal filter. The 5 dB higher than normal at the filter input with the KNB2 removed and jumpered is about right, the KNB2 contains a 6 dB pad which is not in the circuit with just a jumper. You may want to measure the filter input and output again with the KNB2 in place to provide a better match for the filter input. Solve the filter loss problem first and then look at the AGC. You may be getting an incorrect reading for the AGC Saturation level unless you ramped up the signal level into the IF amp to compensate for the filter loss and as a result are not able to saturate the AGC. The S-meter readings will follow the AGC action directly (output of Control Board U2A) except for differences in the resistances following the op amp output, so if your S-meter is responding in a somewhat normal fashion, the AGC voltage applied should also follow - all the rest of the circuitry is insode the IF amp chip. 73, Don W3FPR -Original Message- Ok about the MC1350 specs, and my noise level is very high, but i am afraid that with less noise there is a problem. I did some more measurements end followed the signal tracing procedure, where i find 2 questionable things: - Crystal filter output seems quite low, it reads 0,17 Vrms, instead of the given 0,35V .. tried this with different BFO settings, no significant difference. The input of the filter is about 2,15 Vrms with a jumper over the NB connector (5 dB more than normal) - AGC @ saturation seems way too low, it reads about 4,3 volts where it should be 6,9V. My opinion is that there is some sort of fault in the AGC circuit, that causes no difference in noise level with AGC on or off, and also a big difference in audio level between a S3 and a S9+ station. I have changed C8 a while ago to stop the receive from muting with AGC off, Is it possible that the ACG oscillator level is too low because of this? The receive seems to hear well, compared to my FT-1000. Just the big difference in audio levels worries me.. Thanks again, Sjoerd PE2SVN -Oorspronkelijk bericht- Van: Don Wilhelm [mailto:[EMAIL PROTECTED] Verzonden: woensdag 30 augustus 2006 14:02 Aan: Sjoerd; elecraft@mailman.qth.net Onderwerp: RE: [Elecraft] K2 AGC problem Sjoerd, If you look at the MC1350 data sheet, you will find the AGC characteristics for operation wiht a 12 volt supply to the chip and that graph indicates that the gain changes almost linearly from 0 dB to 20dB with an AGC voltage change from 5 to 6 volts, or 10 dB for a 500 mV change, and the rate of change increases abruptly above the 6 volt level. However, the K2 uses that IF amplifier chip at an 8 volt supply, so as a rough guess, the voltages should be multiplied by a factor of 2/3. I have not attempted to characterize this amplifier at an 8 volt supply. Fact 2 - the gain of the IF Amp is governed by the current rather than the voltage into the AGC pin, so you should conclude that there are several dependencies that will modify the actual voltage required for a given gain. I would suggest that you set the AGC Threshold somewhere between 3.7 and 3.8 volts as measured at Control Board U2 pin 5. You may end up with some slight reduction of gain between AGC on and AGC off, but lower voltage here will tend to produce problems with CAL S HI and CAL S LO settings. If you are willing to live with the consequences of using a voltage lower than 3.7 volts to produce less change between AGC ON/OFF, then you must accept the fact that you will have a weaker AGC gain reduction overall, and your S-meter may produce readings that are different from the norm. You may not have any problem at all, only a consequence of the AGC action produced by your high noise level. 73, Don W3FPR -Original Message- Hello all, Just some added info abt my K2's problem. Measured Vagc at pin 5 of the IF amp: -No antenna connected AGC on: 3.83V -no antenna connected AGC off: 3.82V -40m antenna connected: 3.90V (my FT-1000D shows abt S5 noise) -XG2 connected :3.99V (50uV level, should be S9) Found a post from N6IZ in 2004 that stated that Vagc varies about 100mV per 10dB. ( http://ac6rm.net/mailarchive/html/elecraft-list/2004-10/msg00085.html ) In my case that says my S9 level is only about 16 dB above noise level... Is there anyone who measured Valc at some point and can tell me if these values are way off? Thanks again, Sjoerd PE2SVN ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list
[Elecraft] K2 AGC problem
Hello all, While operating my K2 and switching between bands a lot i noticed my AGC is a bit strange. When trying to set the AGC treshold following Don FPR's instructions i find that the noise level is not changing with the AGC treshold pot with both preamp on and off. There is a difference in noise level between preamp on or off but there not enough noise to trigger the AGC, even with preamp on. Could this be a lack of gain in the receiver or is the ALC circuit wrong? S-meter seems OK to me and the S-meter readings do change with the ALC treshold. Hope to get this nice toy even better.. 73, Sjoerd, PE2SVN ___ 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
[Elecraft] K2 AGC problem on 40m
Hi all, i would lik evening I reconized a AGC problem on 40m band. My signal meter shows S8 to S9 and it sounds like RF-Gain is turned counter clockwise. If i use ATT to reduce the signal level it does not help. The signals will drop down but it still sounds like AGC is to high. I assume it is related to the big signals from broadcast band here in europe. However, further I am not sure if my ALC is working correct. I recoginized following : If I disconnect my antenna from K2 and turn AGC ON/OFF I hear a recognizable difference. I tried to adjust R1 to get the same level. In my case I got the same level if R1 is set to the minimum value. If I do so it looks like the RF- Gain pot has no effect anymore. I assume this is not the intention. I turned it back to the recommended value to get 3.8 volts now. Any ideas where I can investigate are welcome. 73 de Joerg (DL3QQ) ___ 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
[Elecraft] K2 AGC problem?
Someone, Don I think, posted a message this week suggesting that the background noise with no antenna connected should be the same with AGC either on or off. I checked mine out of curiosity and discovered that mine was quieter with AGC on. Before making adjustments to R1, I thought I'd run through the AGC voltage checks in the manual to see what they looked like. With RF gain at maximum, pin 5 of U2 = 3.8vdc I turned to Troubleshooting/Signal Tracing (Appendix E, page11) and made the following measurements on the control board: Using the XG2 signal generator, 7040khz @ 50uv Test 1, XG2 off, RF Gain MAX U2 pin 1 = 3.41vdc - expected 3.6 Test 2, XG2 off, RF Gain MIN U2 pin 1 = 4.50vdc - expected 4.6 Test 3, XG2 on, RF Gain MIN U2 pin 1 = 4.50vdc - expected 6.9 (VFO adjusted for max) U2 pin 5 = 4.89vdc - expected 5.0 In test 3, U2 pin 1 is 2.5vdc too low. Just for grins, I compared the voltages on U2 pins 1 3 at various RF Gain settings and I found the same voltages on both pins; pin 1 seems to be tracking pin 3 accurately; I think this is OK. Using an RF probe, I measured the anode of D1 and found 65mv with XG2 off and 110mv with XG2 on, a 45mv swing. Using an DMM, I measured the cathode of D1 and found 4.73vdc with XG2 off and 4.86vdc with XG2 on. Q12 measures: C = 7.9vdc E = 4.5vdc B = 4.5vdc I'm inclined to believe Q12 may be defective. Before I order parts, though, thought I'd check with you folks and see if I'm even in the ball park. ___ 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 AGC problem?
Matt, At this point, I don't think anything is wrong with your AGC circuit. Re-check the TEST 3 readings with the RF Gain set to MAX and I believe you will see readings a bit closer to the Expected values (I think a step is missing here to tell you to set the RF Gain to max). The 'key' is that the bold print line says that you are testing the AGC at saturation - and with the RF Gain set at minimum, there is no way the AGC will saturate unless you have a VERY strong signal - even the 50 uV from the XG1 is not adequate to saturate the AGC (saturation is S-9 + 40 dB or more - XG1 is only S-9), so do expect a voltage somewhat lower than 6.9 volts. Your results are consistent with what I would expect with the RF Gain at minimum. Your 8 volt supply seems to be actually at 7.9 volts, so you can expect your measurements to be a bit lower than those shown in the manual (they are based on an 8 volt supply level). If you have reasonable 'action' on your S-meter, the AGC circuits are working. Yes, I was the one suggesting the AGC Threshold optimization. 73, Don W3FPR -Original Message- Someone, Don I think, posted a message this week suggesting that the background noise with no antenna connected should be the same with AGC either on or off. I checked mine out of curiosity and discovered that mine was quieter with AGC on. Before making adjustments to R1, I thought I'd run through the AGC voltage checks in the manual to see what they looked like. With RF gain at maximum, pin 5 of U2 = 3.8vdc I turned to Troubleshooting/Signal Tracing (Appendix E, page11) and made the following measurements on the control board: Using the XG2 signal generator, 7040khz @ 50uv Test 1, XG2 off, RF Gain MAX U2 pin 1 = 3.41vdc - expected 3.6 Test 2, XG2 off, RF Gain MIN U2 pin 1 = 4.50vdc - expected 4.6 Test 3, XG2 on, RF Gain MIN U2 pin 1 = 4.50vdc - expected 6.9 (VFO adjusted for max) U2 pin 5 = 4.89vdc - expected 5.0 In test 3, U2 pin 1 is 2.5vdc too low. Just for grins, I compared the voltages on U2 pins 1 3 at various RF Gain settings and I found the same voltages on both pins; pin 1 seems to be tracking pin 3 accurately; I think this is OK. Using an RF probe, I measured the anode of D1 and found 65mv with XG2 off and 110mv with XG2 on, a 45mv swing. Using an DMM, I measured the cathode of D1 and found 4.73vdc with XG2 off and 4.86vdc with XG2 on. Q12 measures: C = 7.9vdc E = 4.5vdc B = 4.5vdc I'm inclined to believe Q12 may be defective. Before I order parts, though, thought I'd check with you folks and see if I'm even in the ball park. -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.344 / Virus Database: 267.10.18/89 - Release Date: 9/2/2005 ___ 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
[Elecraft] K2 AGC problem
Hi, My K2 has been working well and I recently noticed that the AGC fast/slow has little or no effect. I suspect it's been this way for quite some time. I made some measurements and when performing the AGC tests on U2 (LM833), I get very close to the expected values for the specified conditions. My next step was to look at the /SLOW AGC line and select fast or slow. When I do this, I get either 4millivolts or 18 millivolts...not what I had expected. I thought this signal was being driven by U6 so I would have expected either a logic 1 or 0. Any comments will be appreciated. Thanks in advance. Mike, WA1SEO ___ 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 AGC problem
Hi, The problem is solved. After thinking about it for a while, and not having the PIC's data sheet, I wondered if the AGC signal was an open collector / drain type. It turns out that pin 1 of the resistor network had never been soldered in by the builder...not me (the builder knows who he is). Upon soldering pin 1, the fast and slow modes of the AGC work fine AND the QSK problem (that I posted about a couple of weeks ago) was cured, too. Now everything seems to work properly. Mike, WA1SEO ___ 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
