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Hello to all,
A annoyance with my k2 is that the voltage reading when I tap the display button reads 1 full volt low comparied to both of my multimeters. Is there a way to adjust for this error? -- Respectfully, William Marshall Denny II AI4CM _______________________________________________ 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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Marshall,
There is no adjustment - The voltage measuring circuits are usually quite accurate (fixed with 1% resistors). 1 volt is a lot of difference. Normally there will be a 0.3 volt difference between the actual power supply voltage and the voltage internal to the K2 because of the voltage drop across the reverse polarity protection diode D10 and there may be a bit of voltage drop across F1 (the resettable fuse). If you really have a 1 volt drop, you should look for a bad solder connection in the DC supply line. Also, where are you measuring the voltage? If you are measuring it directly at the power supply, examine the connecting cable carefully and be certain its connection to the power supply is tight - loose connections will cause a significant voltage drop which varies with the current drawn. 73, Don W3FPR William Marshall Denny II wrote: > Hello to all, > A annoyance with my k2 is that the voltage reading when I tap the > display button reads 1 full volt low comparied to both of my multimeters. > Is there a way to adjust for this error? > _______________________________________________ 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 William Denny
William Marshall Denny II wrote:
> A annoyance with my k2 is that the voltage reading when I tap the > display button reads 1 full volt low comparied to both of my multimeters. > Is there a way to adjust for this error? The reading when you tap the display button is the voltage read inside the K2 after the protective diode. Are you measuring the voltage of the external power supply feeding the K2 with your multimeters? If so, you can expect a difference of about 0.7 volts (or about 0.3 in newer K2's or ones that are using the newer low voltage drop diode). -- Cheers! Kevin. http://www.ve3syb.ca/ |"What are we going to do today, Borg?" Owner of Elecraft K2 #2172 |"Same thing we always do, Pinkutus: | Try to assimilate the world!" #include <disclaimer/favourite> | -Pinkutus & the Borg _______________________________________________ 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-4
I am experiencing the same problem with my K3. Using the factory supplied power lead. I measure a 1 volt drop between the power supply terminals and the K3 voltage reading at 100watts input (15.68 amps). I suspect most of the drop is from the power lead and if so, seems a little excessive. I'll measure directly across the PL to confirm this. Later Bill Harris w7kxb > Date: Wed, 5 Mar 2008 13:05:00 -0500 > From: [hidden email] > To: [hidden email] > Subject: Re: [Elecraft] voltage > CC: [hidden email] > > Marshall, > > There is no adjustment - The voltage measuring circuits are usually > quite accurate (fixed with 1% resistors). > > 1 volt is a lot of difference. Normally there will be a 0.3 volt > difference between the actual power supply voltage and the voltage > internal to the K2 because of the voltage drop across the reverse > polarity protection diode D10 and there may be a bit of voltage drop > across F1 (the resettable fuse). > If you really have a 1 volt drop, you should look for a bad solder > connection in the DC supply line. > > Also, where are you measuring the voltage? If you are measuring it > directly at the power supply, examine the connecting cable carefully and > be certain its connection to the power supply is tight - loose > connections will cause a significant voltage drop which varies with the > current drawn. > > 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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Bill,
Be certain you make the measurement under load. Measure both at the APP power connector at the K3 end and at the power supply (with the same load current). You can then calculate the voltage drop on the lead and also the resistance of the path. Compare the resistance with a wire table for the same gauge wire (remember that the total conductor path length is twice the cable length) to determine whether the resistance in your cable is excessive. 73, Don W3FPR Bill Harris wrote: > I am experiencing the same problem with my K3. Using the factory > supplied power lead. I measure a 1 volt drop between the power supply > terminals and the K3 voltage reading at 100watts input (15.68 amps). I > suspect most of the drop is from the power lead and if so, seems a > little excessive. I'll measure directly across the PL to confirm this. > > Later > Bill Harris w7kxb > > > Date: Wed, 5 Mar 2008 13:05:00 -0500 > > From: [hidden email] > > To: [hidden email] > > Subject: Re: [Elecraft] voltage > > CC: [hidden email] > > > > Marshall, > > > > There is no adjustment - The voltage measuring circuits are usually > > quite accurate (fixed with 1% resistors). > > > > 1 volt is a lot of difference. Normally there will be a 0.3 volt > > difference between the actual power supply voltage and the voltage > > internal to the K2 because of the voltage drop across the reverse > > polarity protection diode D10 and there may be a bit of voltage drop > > across F1 (the resettable fuse). > > If you really have a 1 volt drop, you should look for a bad solder > > connection in the DC supply line. > > > > Also, where are you measuring the voltage? If you are measuring it > > directly at the power supply, examine the connecting cable carefully > and > > be certain its connection to the power supply is tight - loose > > connections will cause a significant voltage drop which varies with the > > current drawn. > > > > 73, > > Don W3FPR > > ------------------------------------------------------------------------ > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.21.4/1313 - Release Date: 3/5/2008 9:50 AM > 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 William Denny
I found this annoying, too, so I did something about it - the idea
is not original to me. I learned about it from J-F VA2VYZ. I changed R10 to be a trimpot: a Bourns 3296W-254 25-turn trimmer. See a photo at http://www.dimebank.com/cak/k6dbg/photos/voltmeter_pot.jpg I adjusted mine so the display voltmeter matches the measured voltage past the diode. 73 de chris K6DBG _______________________________________________ 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 William Denny
K6DBG wrote:
"I adjusted mine so the display voltmeter matches the measured voltage past the diode." That's an interesting idea; however if you ever go back to assembly steps using the internal DVM, you would have to compensate for the offset you put in (assuming it is a pure offset and no gain factor is involved), or use an external DVM for those steps. I prefer having my internal DVM reading the true voltage. 73, Chuck NI0C K2 s/n 5853; K3 ordered _______________________________________________ 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 William Denny
Chuck NI0C wrote:
> K6DBG wrote: > "I adjusted mine so the display voltmeter matches the measured > voltage past the diode." > > That's an interesting idea; however if you ever go back to assembly > steps using the internal DVM, you would have to compensate for the > offset you put in (assuming it is a pure offset and no gain factor is > involved), or use an external DVM for those steps. > > I prefer having my internal DVM reading the true voltage. I think you misunderstand - the adjustment is specifically to have the display show the true voltage. The K2 uses a voltage divider (R9, R10) into an op amp (U3B) to determine the displayed voltage; the resistors used are "only" 1%, so there is some inaccuracy in the resulting "V SENSE". Changing R10 to a trimpot allows me to set the bridge accurately. 73, chris _______________________________________________ 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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Gentlemen,
But the question really is: What is the 'true' voltage. IMHO, the true voltage is the voltage that is present inside the K2, For others, the true voltage might be the voltage applied to the K2. The stock K2 will indicate the actual voltage inside the K2, but by adjusting the resistor, it can be skewed to indicate the power supply voltage - however, that will skew the readings if one attempts to use the internal voltmeter to read voltages with the probe - the readings will be skewed by the amount of 'correction', Each to his own choice. 73, Don W3FPR Chris Kantarjiev wrote: > Chuck NI0C wrote: > > >> K6DBG wrote: >> "I adjusted mine so the display voltmeter matches the measured >> voltage past the diode." >> >> That's an interesting idea; however if you ever go back to assembly >> steps using the internal DVM, you would have to compensate for the >> offset you put in (assuming it is a pure offset and no gain factor is >> involved), or use an external DVM for those steps. >> >> I prefer having my internal DVM reading the true voltage. >> > > I think you misunderstand - the adjustment is specifically to have > the display show the true voltage. > > The K2 uses a voltage divider (R9, R10) into an op amp (U3B) to > determine the displayed voltage; the resistors used are "only" 1%, > so there is some inaccuracy in the resulting "V SENSE". Changing > R10 to a trimpot allows me to set the bridge accurately. > > 73, > chris > _______________________________________________ > 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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In reply to this post by William Denny
> The stock K2 will indicate the actual voltage inside the K2,
Mine didn't. It was off by about 0.3v, which is why I made the fix... I did *not* try to make it read the supply voltage applied at the back of the radio. 73, chris _______________________________________________ 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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