KPA100 D1-D8 voltages
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I've completed construction of my KPA100 and am doing
final voltage checks listed in the manual on p.46. My KPA100 as bought was a rev. C kit, but prior to construction I purchased parts to build it as a rev. D. Apparently I was not thorough enough in annotating my manual, as I was looking for the high voltage from the bias supply at the cathode of D13, but in the rev. D manual, the test point is changed to the junction of C77 and R11. Before realizing this, I had the heat sink removed and was testing voltage on D1-D8. Although the voltage at junction of C77 and R11 was within spec, many of the voltages at D1-D8 are significantly different from the tables in the manual. I don't know if I should be concerned about this or not since the final high voltage is within spec (now that I'm measuring at the right test point), as is the negative supply for the RS-232. Here's a list of my measurements at D1-D8. Spec Mine Diode Anode Cathode Anode Cathode D1 32 130 21.1 138 D2 84 32 89.0 20.9 D3 21 84 18.1 88.7 D4 36 21 38.2 17.1 D5 24 36 15.9 38.2 D6 13.7 24 13.5 16.0 D7 -22 -8.8 -24.1 -1.1 D8 -8.8 0 -1.1 0 Any insight would be appreciated. -Ben K1NT _______________________________________________ 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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Ben,
THose voltages are not 'spec', but they are guidelines for troubleshooting. The oscillator activity will vary a lot from one unit to another, and a 10% variation either way from the values stated is usually OK - The important voltages are at the D1 cathode and the D7 anode. Two points - 1) there is a new Diode voltage chart in the current level errata sheet - download it and use that chart. 2) is the R4 value on your KPA100 board 100k? If not change it to 100k and that will drop your D1-D8 voltages down a bit if your current R4 value is 39k. 73, Don W3FPR > -----Original Message----- > I don't know if I should be concerned about this or > not since the final high voltage is within spec (now > that I'm measuring at the right test point), as is the > negative supply for the RS-232. Here's a list of my > measurements at D1-D8. > > Spec Mine > Diode Anode Cathode Anode Cathode > D1 32 130 21.1 138 > D2 84 32 89.0 20.9 > D3 21 84 18.1 88.7 > D4 36 21 38.2 17.1 > D5 24 36 15.9 38.2 > D6 13.7 24 13.5 16.0 > D7 -22 -8.8 -24.1 -1.1 > D8 -8.8 0 -1.1 0 > > Any insight would be appreciated. > > -Ben K1NT > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.16.8/621 - Release Date: 1/9/2007 1:37 PM _______________________________________________ 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 |
KPA100 D13 Cathode High Voltage
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In reply to this post by Ben Hofmann K1NT
All,
I performed the voltage checks at the KPA100 Test Points as stated on page 43 of the KPA100 manual (rev. C, Feb. 11, 2004). The D13 cathode should have a voltage between 90 and 150 volts; the measured voltage is 175 volts, which seems a little high. Also, the voltage measured at U4 pin is -30 volts, but the manual indicates the voltage range should be between -5 and -25 volts. Consulted the schematic and it appears as if the voltage from pin 8 of U4 supplies the High Voltage Bias Supply circuit. Mesaured the voltage at C44 as 45 volts, but schematic indicates it should be 30 volts. Is 175 volts too high a voltage at the D13 cathode? R4 is 39K. Any suggestions or help would be greatly appreciated! Michael KI5E _________________________________________________________________ Get live scores and news about your team: Add the Live.com Football Page www.live.com/?addtemplate=football&icid=T001MSN30A0701 _______________________________________________ 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 |
RE: KPA100 D13 Cathode High Voltage
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Michael, change R4 to 100K. That change is necessary to keep from applying
excessive voltage to some components in the KPA100. Your amplifier may work for indefinitely with the higher voltage (or not), but you are over-stressing some parts. Ron AC7AC -----Original Message----- All, I performed the voltage checks at the KPA100 Test Points as stated on page 43 of the KPA100 manual (rev. C, Feb. 11, 2004). The D13 cathode should have a voltage between 90 and 150 volts; the measured voltage is 175 volts, which seems a little high. Also, the voltage measured at U4 pin is -30 volts, but the manual indicates the voltage range should be between -5 and -25 volts. Consulted the schematic and it appears as if the voltage from pin 8 of U4 supplies the High Voltage Bias Supply circuit. Mesaured the voltage at C44 as 45 volts, but schematic indicates it should be 30 volts. Is 175 volts too high a voltage at the D13 cathode? R4 is 39K. Any suggestions or help would be greatly appreciated! Michael KI5E _______________________________________________ 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 |
K2 Frequency Stability and Invitation to DC Area K2 Owners
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In reply to this post by Michael Haygood
I've posted two series of frequency stability measurements for my K2
(SN 5689) that might be of interest to the group. The data can be seen at http://www.cliftonlaboratories.com/Updates.htm under the 11 January 2007 entry. I also wonder if there are any Washington DC area K2 owners that would be interested in seeing how their K2 measures in my basement lab. I'm in Fairfax County Virginia and would be interested in looking at receiver sensitivity and transmitted emissions, although we can measure other things as well. (Power measurements included, although accurately measuring RF output power is a non-trivial task.) If you are interested, contact me via E-mail. 73 de Jack K8ZOA www.cliftonlaboratories.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 |
RE: KPA100 D13 Cathode High Voltage
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In reply to this post by Michael Haygood
Michael,
Increase R4 to 100K and the voltages will drop. If you read the KPA100UPKT instructions carefully you will find the instruction to check R4 and change it to 100k if necessary in 'PART IV:Other Changes' 73, Don W3FPR > -----Original Message----- > > I performed the voltage checks at the KPA100 Test Points as > stated on page > 43 of the KPA100 manual (rev. C, Feb. 11, 2004). The D13 cathode should > have a voltage between 90 and 150 volts; the measured voltage is > 175 volts, > which seems a little high. Also, the voltage measured at U4 pin is -30 > volts, but the manual indicates the voltage range should be > between -5 and > -25 volts. > > Consulted the schematic and it appears as if the voltage from pin 8 of U4 > supplies the High Voltage Bias Supply circuit. Mesaured the > voltage at C44 > as 45 volts, but schematic indicates it should be 30 volts. > > Is 175 volts too high a voltage at the D13 cathode? R4 is 39K. > > Any suggestions or help would be greatly appreciated! > > Michael > KI5E > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.16.9/622 - Release Date: 1/10/2007 2:52 PM _______________________________________________ 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 |
K2 Frequency Stability Data and AGC Action
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In reply to this post by Michael Haygood
I've finished additional K2 receiver measurements and have posted them
to my web site, www.cliftonlaboratories.com. Specifically: 1. Frequency stability from a cold soaked start (K2 left outside overnight, with a temperature low of 20 degrees F). This data can be viewed at http://www.cliftonlaboratories.com/k2_freq_stability.htm 2. AGC performance, a comparison of audio output versus RF input for the K2, the Drake R7 and the Racal RA6790/GM. This data can be viewed at http://www.cliftonlaboratories.com/receiver_agc_curves.htm. The measured data goes a long way towards explaining why a K2 receiver sounds "different" than many other receivers. There's also an update to measuring AM modulation percentages and other things. The best way to find recent changes to my site is to start at the updates page. http://www.cliftonlaboratories.com/Updates.htm Jack K8ZOA K2 5689 www.cliftonlaboratories.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 |
RE: K2 Frequency Stability Data and AGC Action
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> I've finished additional K2 receiver measurements and have posted them to
my web site, > www.cliftonlaboratories.com. Very interesting results, in particular the AGC performance curve. I wonder about the statement "In an ideal receiver, once the threshold point is passed, there will be little or no change in audio output with changes in signal level." The way people speak so highly of the AGC action of their K2s seems to contradict this. But then maybe this is called the ideal curve just because it is easy to comprehend and draw for engineers. I have worked enough with acoustics and psychoacoustics to have great respect for the ear and our hearing. It is a very subtle instrument that is not so easy to quantify in a simple curve. Maybe design of AGC characteristics could learn something from the psychoacoustics that is built into all modern sound coders, like mp3 and its descendants? 73 Sverre LA3ZA Unofficial Guide to K2 Modifications http://www.qslnet.de/member/la3za/K2/mod.html -- I am using the free version of SPAMfighter for private users. It has removed 1373 spam emails to date. Paying users do not have this message in their emails. Get the free SPAMfighter here: http://www.spamfighter.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 |
Re: K2 Frequency Stability Data and AGC Action
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That's a good point. In the AM broadcast receiver world, the ideal AGC
action, I believe, is to maintain the IF at a constant level into the detector, so (1) the detector does not overload if you are close to the transmitter; and (2) so that the demodulated audio is always the same level, regardless of the signal strength, for a given modulation waveform. In that regard, the classic AGC curves found in the Racal and Drake receivers, as well as others that I've looked at match the ideal action. No AGC action up to a threshold and then very aggressive AGC action above that threshold, so that 100 dB of signal level change produces essentially zero change in audio output. Whether the behavior desired in the AM broadcast world should be carried over to amateur radio is an interesting question. The fact that most receivers are designed one way does not mean that is necessarily the best way. Of course, the reason most receivers are designed that way may be because it is the easiest from an engineering prospective, or it may be a case where it also provides the optimum user experience. Jack K8ZOA Sverre Holm wrote: >> I've finished additional K2 receiver measurements and have posted them to >> > my web site, > >> www.cliftonlaboratories.com. >> > > Very interesting results, in particular the AGC performance curve. > > I wonder about the statement "In an ideal receiver, once the threshold point > is passed, there will be little or no change in audio output with changes in > signal level." The way people speak so highly of the AGC action of their K2s > seems to contradict this. But then maybe this is called the ideal curve just > because it is easy to comprehend and draw for engineers. > > I have worked enough with acoustics and psychoacoustics to have great > respect for the ear and our hearing. It is a very subtle instrument that is > not so easy to quantify in a simple curve. Maybe design of AGC > characteristics could learn something from the psychoacoustics that is built > into all modern sound coders, like mp3 and its descendants? > > > 73 > > Sverre > LA3ZA > > Unofficial Guide to K2 Modifications > http://www.qslnet.de/member/la3za/K2/mod.html > > 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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