K2/100 current consumption problem
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K2/100 current consumption problem
 
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I've just noticed that our club's K2/100 (#3764) draws excessive current on
topband. Going through the bands my own K2/100 (#4368) draws between approx. 15-19A at full power setting, (circa 100W o/p). The club rig draws between approx. 16-20A in the same test, but on topband the current consumption is 27A !! I did not build the clubs rig, but the ham who built it has built several K2's. Both rigs have the latest mods/screening/upgrades, including the PA instability fix for 80m. There does not appear to be any instability on topband - I've checked on a scope and spectrum analyser. It's possible the club's PA missed out on a mod early in it's life? Any ideas please? Looks like it's short of some L or C somewhere. Thanks, Fraser G4BJM _________________________________________________________________ Express yourself with cool new emoticons http://www.msn.co.uk/specials/myemo _______________________________________________ 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: K2/100 current consumption problem
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What does the K2 w/o the PA pull compared to the other bands? It could be
lack of drive, making the 100w PA less efficient. Are these measurements made on a dummy load or the antenna? Is a tuner involved? Were the PA mounting screws retightened as required? Is the PA and rig in the same box? NRE/COLE Test Center OH-3 pcarter<at>gcfn.org or wd8qwr<at>arrl.net Philip L. Carter, WD8QWR wd8qwr@w8cqk.#cmh.oh.usa.na _______________________________________________ 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: K2/100 current consumption problem
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In reply to this post by Fraser Robertson
Fraser,
Not a mod, but an alignment may have been overlooked. The K2 bandpass filter is shared between 160 and 80 meters, so it often must be adjusted to a compromise setting to balance between the two bands. Adjust the bandpass filter for a peak on 160 meters, and then adjust it for a peak on 80 meters and observe how much difference there is. Then initially set it to a mid-point and then if desired 'tweak' it a bit to achieve the best balance on both bands. 73, Don W3FPR > -----Original Message----- > > I've just noticed that our club's K2/100 (#3764) draws excessive > current on > topband. > > Going through the bands my own K2/100 (#4368) draws between > approx. 15-19A > at full power setting, (circa 100W o/p). The club rig draws > between approx. > 16-20A in the same test, but on topband the current consumption is 27A !! > > I did not build the clubs rig, but the ham who built it has built several > K2's. > > Both rigs have the latest mods/screening/upgrades, including the PA > instability fix for 80m. There does not appear to be any instability on > topband - I've checked on a scope and spectrum analyser. > > It's possible the club's PA missed out on a mod early in it's life? > > Any ideas please? Looks like it's short of some L or C somewhere. > > Thanks, Fraser G4BJM > _______________________________________________ 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: K2/100 current consumption problem
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In reply to this post by Fraser Robertson
Fraser,
Just checked my K2/100 setup. For 100w it draws 20Amps, so something is wrong. I would check the KPA100 160m low pass filter components. If you have access to an antenna analyser such as a MFJ then use that with the dummy load. If not use a signal generator along with your scope. 73 Stewart G3RXQ On Tue, 01 Mar 2005 14:19:42 +0000, Fraser Robertson wrote: > I've just noticed that our club's K2/100 (#3764) draws excessive current on > > topband. > > Going through the bands my own K2/100 (#4368) draws between approx. 15-19A > at full power setting, (circa 100W o/p). The club rig draws between approx. > 16-20A in the same test, but on topband the current consumption is 27A !! > > I did not build the clubs rig, but the ham who built it has built several > K2's. > > Both rigs have the latest mods/screening/upgrades, including the PA > instability fix for 80m. There does not appear to be any instability on > topband - I've checked on a scope and spectrum analyser. > > It's possible the club's PA missed out on a mod early in it's life? > > Any ideas please? Looks like it's short of some L or C somewhere. > > Thanks, Fraser G4BJM > > _________________________________________________________________ > Express yourself with cool new emoticons http://www.msn.co.uk/specials/myemo > > _______________________________________________ > 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 |
Re: K2/100 current consumption problem
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>>Going through the bands my own K2/100 (#4368) draws between approx. 15-19A
>>at full power setting, (circa 100W o/p). The club rig draws between approx. >>16-20A in the same test, but on topband the current consumption is 27A !! When typing "same test" do you mean "with same antennas and other setup"? Sometimes current measurement fails due to rf. Maybe this is not the real problem because your problem arises in 1.8MHz. Rolf oh6kxl _______________________________________________ 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: K2/100 current consumption problem
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Sorry I should have said that the tests were into a 50R dummy load. Thanks
for the replies so far. Stewart - thanks - worth shecking the LPF components. Don - I don't understand why the BPF alignment would cause this problem? 73 Fraser G4BJM >From: "Rolf Moberg, OH6KXL" <[hidden email]> >When typing "same test" do you mean "with same antennas and other setup"? >Sometimes current measurement fails due to rf. Maybe this is not the real >problem because your problem arises in 1.8MHz. > >Rolf >oh6kxl _________________________________________________________________ It's fast, it's easy and it's free. Get MSN Messenger today! http://www.msn.co.uk/messenger _______________________________________________ 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: K2/100 current consumption problem
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In reply to this post by Philip L Carter
Thanks Philip, I will check the current of the base K2. The PA is in the
same box. No tuner involved. I would expect lack of drive would result in low output and hence current? I don't understand your point re the pa screws, surely that would cause overheating of the transistors on all bands? Thanks / 73, Fraser G4BJM >From: Philip L Carter <[hidden email]> > >What does the K2 w/o the PA pull compared to the other bands? It could be >lack of drive, making the 100w PA less efficient. Are these measurements >made on a dummy load or the antenna? Is a tuner involved? Were the PA >mounting screws retightened as required? Is the PA and rig in the same >box? > > _________________________________________________________________ Want to block unwanted pop-ups? Download the free MSN Toolbar now! http://toolbar.msn.co.uk/ _______________________________________________ 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: K2/100 current consumption problem
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In reply to this post by Fraser Robertson
Oops, I should have said thanks to Gary too - his reply somehow ended up in
the wrong folder here. The LPF and components around T1 & T2 seem to be the place to look. 73 Fraser _________________________________________________________________ Express yourself with cool new emoticons http://www.msn.co.uk/specials/myemo _______________________________________________ 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: K2/100 current consumption problem - update
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In reply to this post by Fraser Robertson
So far I haven't found anything wrong as such on #3764:
The LPF components appear fine (value and condition), and check out ok with an MFJ analyser for SWR on receive. T1 and T2 and associated components appear ok. One thing; C83 is 1000pF, not 1200pF as per circuit. However I tried padding that with a 220pF SM and it made no difference. Looks like 1000pF was supplied with the kit. I've realigned the BPF on 160/80m, which was pretty much ok anyway. I've re-adjusted the bias, which was also ok. I've readjusted the pwr sense pot, again was ok. With the PA disabled the base K2 draws about 2.5A @ 10W op on all bands. With the PSU set to exactly 13.8V, and measuring the current (V across 10x0R1 6W in parallel, in series with V+) I get the following, into a 50R load. Current on the PSU display reads similar. Set power W Current A 160m Current A 80m 50 14 14 60 15 15 70 16.5 16.5 80 18 18 90 24 19 100 27 20 110 29 21 The actual power out is similar to the set power, to about 10%. So topband behaves ok up to about 80W op. This also happens from a cold start, so I don't think it's thermal runaway. No instabilities are apparent on a scope or spec. an. Any suggestions appreciated. Thanks / 73 Fraser G4BJM _________________________________________________________________ It's fast, it's easy and it's free. Get MSN Messenger today! http://www.msn.co.uk/messenger _______________________________________________ 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: K2/100 current consumption problem - update
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Fraser,
This is a very very long shot and probably daft! I see that the current drawn on 160m tracks that drawn on 80m until the RF output passes 80w.going up.From this I think that it is safe to say that the "bad" KPA100 is working as it should to that power output level. Above that it is either starting to flat-top for X reasons or its standing DC bias is changing perhaps towards Class A or the driver has run out of steam. Let me focus on bias change. Is it poissible that 160m RF above a certain output power level mucks up the PA bias oscillator or that some circuit(s) in the bias supply resonate at 160m thereby changing the DC bias to the PA.? There is a lot of PA output RF around, but it might be worthwhile to measure the DC bias voltage as you run up the PA power. Capacitor tolerances alone would move such resonances around greatly. Just a thought. 73, Geoff. GM4ESD ----- Original Message ----- From: "Fraser Robertson" <[hidden email]> To: <[hidden email]>; <[hidden email]> Cc: <[hidden email]> Sent: Thursday, March 03, 2005 2:21 PM Subject: Re: [Elecraft] K2/100 current consumption problem - update > So far I haven't found anything wrong as such on #3764: > > The LPF components appear fine (value and condition), and check out ok with > an MFJ analyser for SWR on receive. > > T1 and T2 and associated components appear ok. One thing; C83 is 1000pF, > not 1200pF as per circuit. However I tried padding that with a 220pF SM and > it made no difference. Looks like 1000pF was supplied with the kit. > > I've realigned the BPF on 160/80m, which was pretty much ok anyway. > > I've re-adjusted the bias, which was also ok. > > I've readjusted the pwr sense pot, again was ok. > > With the PA disabled the base K2 draws about 2.5A @ 10W op on all bands. > > With the PSU set to exactly 13.8V, and measuring the current (V across > 10x0R1 6W in parallel, in series with V+) I get the following, into a 50R > load. Current on the PSU display reads similar. > > Set power W Current A 160m Current A 80m > 50 14 14 > 60 15 15 > 70 16.5 16.5 > 80 18 18 > 90 24 19 > 100 27 20 > 110 29 21 > > The actual power out is similar to the set power, to about 10%. So > topband behaves ok up to about 80W op. This also happens from a cold > so I don't think it's thermal runaway. > > No instabilities are apparent on a scope or spec. an. > > Any suggestions appreciated. Thanks / 73 Fraser G4BJM > _______________________________________________ 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 Fraser Robertson
Fraser Robertson wrote:
> One thing; C83 is > 1000pF, not 1200pF as per circuit. However I tried padding that with a > 220pF SM and it made no difference. Looks like 1000pF was supplied with > the kit. Hi Fraser, The change from 1200 to 1000 was made after the field test. It improves efficiency on 10 meters. It shouldn't have any effect on 160. 1000 is correct. I admit to being mystified by your problem! -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ 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: K2/100 current consumption problem - update
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In reply to this post by Fraser Robertson
Thanks Geoff, the TR bias HV is 139V on RX. On TX at 70W out it's about
118V on 160m and 80m. With power flat out it's 113V on 80m and 109V on 160m. So I think that's ok. The voltage on U7B pin 5 and 6 is identical on 160m and 80m at full power at 675mV, so I think the PA bias current is behaving. G3VTT suggested the transformers, but they have the correct number of turns, including the po/swr sensor T4. Thanks / 73 Fraser G4BJM >From: "Geoffrey Mackenzie-Kennedy" <[hidden email]> >To: "Fraser Robertson" <[hidden email]> >CC: "Elecraft Discussion List" <[hidden email]> >Subject: Re: [Elecraft] K2/100 current consumption problem - update >Date: Thu, 3 Mar 2005 15:26:48 -0000 > >Fraser, > >This is a very very long shot and probably daft! I see that the current >drawn on 160m tracks that drawn on 80m until the RF output passes 80w.going >up.From this I think that it is safe to say that the "bad" KPA100 is >working >as it should to that power output level. Above that it is either starting >to >flat-top for X reasons or its standing DC bias is changing perhaps towards >Class A or the driver has run out of steam. > >Let me focus on bias change. Is it poissible that 160m RF above a certain >output power level mucks up the PA bias oscillator or that some circuit(s) >in the bias supply resonate at 160m thereby changing the DC bias to the >PA.? >There is a lot of PA output RF around, but it might be worthwhile to >measure >the DC bias voltage as you run up the PA power. > >Capacitor tolerances alone would move such resonances around greatly. > >Just a thought. > >73, >Geoff. >GM4ESD > >----- Original Message ----- >From: "Fraser Robertson" <[hidden email]> >To: <[hidden email]>; <[hidden email]> >Cc: <[hidden email]> >Sent: Thursday, March 03, 2005 2:21 PM >Subject: Re: [Elecraft] K2/100 current consumption problem - update > > > > So far I haven't found anything wrong as such on #3764: > > > > The LPF components appear fine (value and condition), and check out ok >with > > an MFJ analyser for SWR on receive. > > > > T1 and T2 and associated components appear ok. One thing; C83 is >1000pF, > > not 1200pF as per circuit. However I tried padding that with a 220pF SM >and > > it made no difference. Looks like 1000pF was supplied with the kit. > > > > I've realigned the BPF on 160/80m, which was pretty much ok anyway. > > > > I've re-adjusted the bias, which was also ok. > > > > I've readjusted the pwr sense pot, again was ok. > > > > With the PA disabled the base K2 draws about 2.5A @ 10W op on all bands. > > > > With the PSU set to exactly 13.8V, and measuring the current (V across > > 10x0R1 6W in parallel, in series with V+) I get the following, into a >50R > > load. Current on the PSU display reads similar. > > > > Set power W Current A 160m Current A 80m > > 50 14 14 > > 60 15 15 > > 70 16.5 16.5 > > 80 18 18 > > 90 24 19 > > 100 27 20 > > 110 29 21 > > > > The actual power out is similar to the set power, to about 10%. So > > topband behaves ok up to about 80W op. This also happens from a cold >start, > > so I don't think it's thermal runaway. > > > > No instabilities are apparent on a scope or spec. an. > > > > Any suggestions appreciated. Thanks / 73 Fraser G4BJM > > > _________________________________________________________________ It's fast, it's easy and it's free. Get MSN Messenger today! http://www.msn.co.uk/messenger _______________________________________________ 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: K2/100 current consumption problem - update
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Fraser,
If you have a 'scope handy, try cranking the power up to 100 watts on 160 and 80 and observing the CW envelope - if you see what looks like weak modulation on the top and bottom of the envelope pattern, you have a low frequency oscillation. If you do have that oscillation, the 'cure' has been discussed on this reflector - on the KPA100, put a 1K resistor across RFC3, and change R4 from 100k to 39k. I have worked on KPA100s having this modulation problem, but never related it to current draw before, but it is worthy of investigation. 73, Don W3FPR > -----Original Message----- > > Thanks Geoff, the TR bias HV is 139V on RX. On TX at 70W out it's about > 118V on 160m and 80m. With power flat out it's 113V on 80m and 109V on > 160m. So I think that's ok. > > The voltage on U7B pin 5 and 6 is identical on 160m and 80m at > full power at > 675mV, so I think the PA bias current is behaving. > > G3VTT suggested the transformers, but they have the correct > number of turns, > including the po/swr sensor T4. > > Thanks / 73 Fraser G4BJM > > _______________________________________________ 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: K2/100 current consumption problem - update
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Thanks Don, there is no instability apparent on a scope or spec an. I've
already done the R4 and RFC3 mods as per latest errata, which cured the 80m instability for me. Unfortunately I'm not sure if this problem was always there, or started when I did the pa upgrade (screening/firmware/swr/R4&RFC3). 73 Fraser >From: "W3FPR - Don Wilhelm" <[hidden email]> >Reply-To: <[hidden email]> >To: "Fraser Robertson" <[hidden email]>,<[hidden email]> >CC: <[hidden email]> >Subject: RE: [Elecraft] K2/100 current consumption problem - update >Date: Thu, 3 Mar 2005 19:05:23 -0500 > >Fraser, > >If you have a 'scope handy, try cranking the power up to 100 watts on 160 >and 80 and observing the CW envelope - if you see what looks like weak >modulation on the top and bottom of the envelope pattern, you have a low >frequency oscillation. If you do have that oscillation, the 'cure' has >been >discussed on this reflector - on the KPA100, put a 1K resistor across RFC3, >and change R4 from 100k to 39k. > >I have worked on KPA100s having this modulation problem, but never related >it to current draw before, but it is worthy of investigation. > >73, >Don W3FPR _________________________________________________________________ Express yourself with cool new emoticons http://www.msn.co.uk/specials/myemo _______________________________________________ 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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