One thing to remember is that the 240 volt power line is not constant voltage. Line voltage varies through the day depending on the overall power load seen by the electric company in your area. So while you may measure 239v now, it may droop or go higher as the overall load varies during the day. That makes it difficult for us to give an absolute value for the tap setting, and also makes it difficult for you to say that any one is always the best. Try one for now, and if it works out in the long run, then keep it! If you start seeing HV high voltage faults, then drop back to a lower voltage tap. As K9YC says, you can help by using the biggest wires you can find, especially for the power cable from the wall to the KPA500. This is especially important at 110V, but applies to 220V as well.
And, for the record, the KPA500 HV fault is at 90 volts. But you don’t really want to get there… Jack Brindle, W6FB Elecraft Engineering > On Mar 22, 2015, at 2:33 PM, Harry Yingst <hlyin...@yahoo.com> wrote: > > > Thank you, That was how it seemed I just wanted to double check. > > That amp seems a bit happier on 240 than 120. > > > > > > From: Jack Brindle <jackbrin...@me.com> > To: Harry Yingst <hlyin...@yahoo.com> > Cc: Elecraft Reflector <elecraft@mailman.qth.net> > Sent: Sunday, March 22, 2015 4:20 PM > Subject: Re: [Elecraft] KPA500 Proper Transformer Tap setting > > The one that keeps the no-load HV in spec and gives you the best performance. > If that is the Red tap, then use that one. > > The two sentences are not in conflict. You should expect a major drop in HV on > key-down due to losses in the power supply. This includes the components in > the KPA500 (transformer, etc), the power cord, plug, wall outlet and wiring > all > the way to the main pole transformer. You can’t do much about most of this, > but making sure the power cord can handle the current without overheating is > a great idea. Of course this problem is worse with a 120V supply than 240V > since the current is proportionately higher. > > So, again, if the red tap gives you better output and keeps the HV within the > 85V > spec under no-load conditions, use it. Make sure it meets both conditions, > though. > > 73, > > Jack B, W6FB > Elecraft Engineering > > > > > >> On Mar 22, 2015, at 1:10 PM, Harry Yingst <hlyin...@yahoo.com >> <mailto:hlyin...@yahoo.com>> wrote: >> >> My line voltage is 239 (which calls for the yellow tap) but on Key down it >> sags to 59v >> >> With the Red Tap it only sags to about 66v (80.7 no key) >> >> >> So The proper tap would be? >> >> >> >> >> >> >> >> >> From: Jack Brindle <jackbrin...@me.com <mailto:jackbrin...@me.com>> >> To: Harry Yingst <hlyin...@yahoo.com <mailto:hlyin...@yahoo.com>> >> Cc: Elecraft Reflector <elecraft@mailman.qth.net >> <mailto:elecraft@mailman.qth.net>> >> Sent: Sunday, March 22, 2015 3:58 PM >> Subject: Re: [Elecraft] KPA500 Proper Transformer Tap setting >> >> Both. The HV is directly proportional to the line voltage. This makes sense, >> since the HV is derived through a linear transformer. >> If your line voltage rises so that it causes the HV to go too high (spec is >> 85, the KPA faults at 90V), then you have set the tap incorrectly. >> Set the tap according to your line voltage as described on page 9 so that it >> gives you nominal HV in the range as described on page 17. >> >> - Jack Brindle, W6FB >> Elecraft Engineering >> >> >> >> >> > On Mar 22, 2015, at 11:49 AM, Harry Yingst via Elecraft >> > <elecraft@mailman.qth.net <mailto:elecraft@mailman.qth.net>> wrote: >> > >> > In the manual on page 9 it shows to set the tap for the line voltage, but >> > on Page 17 under Note it states >> > "The KPA500 operates to full specifications when the HV under full load >> > isbetween 60V and 85V as shown on the LCD (Tap HV to display the >> > voltageunder CW “key down” conditions at full power). The maximum voltage >> > is setusing transformer taps as described on pg. 9." >> > Which is correct? >> >> > >> > >> > ______________________________________________________________ >> > Elecraft mailing list >> > Home: http://mailman.qth.net/mailman/listinfo/elecraft >> > <http://mailman.qth.net/mailman/listinfo/elecraft> >> > Help: http://mailman.qth.net/mmfaq.htm <http://mailman.qth.net/mmfaq.htm> >> > Post: mailto:Elecraft@mailman.qth.net <mailto:Elecraft@mailman.qth.net> >> > >> > This list hosted by: http://www.qsl.net <http://www.qsl.net/> >> > Please help support this email list: http://www.qsl.net/donate.html >> > <http://www.qsl.net/donate.html> >> > Message delivered to jackbrin...@me.com <mailto:jackbrin...@me.com> >> >> >> > > > ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
