KPA500 finals blown
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KPA500 shut off with a bang while operating RTTY @300W.
Antenna is a steppir beam. On opening the KPA500,found 2 ceramic? caps of VRF2933 adrift with underside of the said caps,black. Have written to support.Is this the first time this has happened in a KPA500? 73 and HNY, Nandu VU2NKS ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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I would like to know what the continous keydown power output rating is. The
manual talks about ICAS. I know when I get on RTTY I does not take long for The fans to come up to full speed running 300 watts. Earl, K4Kay -----Original Message----- From: Elecraft [mailto:[hidden email]] On Behalf Of Nand Kishore Sent: Thursday, January 21, 2016 4:29 AM To: elecraft Subject: [Elecraft] KPA500 finals blown KPA500 shut off with a bang while operating RTTY @300W. Antenna is a steppir beam. On opening the KPA500,found 2 ceramic? caps of VRF2933 adrift with underside of the said caps,black. Have written to support.Is this the first time this has happened in a KPA500? 73 and HNY, Nandu VU2NKS ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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The recent article in February QST describing the CESSB mode is of
interest. Just wondering if that mode can or will be added to the code operating the K3S? Also, wondering if the higher duty cycle of the CESSB mode will exceed the ratings of the PA stage and that of the KPA500? From what I read it seems that most SSB rated amps, past and present, may have inadequate ratings for the higher duty cycle. Thoughts? 73 Bob, K4TAX ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by efortner
As applied to solid-state transmitters, ICAS does not imply reduced
device life, as unlike vacuum tubes, the RF power devices are not regarded as consumables. Rather, ICAS in a solid-state environment implies de-rating to keep the device junction and case temperatures within their maximum ratings. Thus, ICAS suggests a limited operating or 'on' period followed by an 'off' or standby period of at least the same or longer duration, whilst CCS assumes continuous, key-down operation at reduced output (assuming the same heatsink area and/or fan air-flow rating for both applications). Typically, a PA cooling system should be designed to keep the device case temperature in the range 70 ~ 80ºC (158 ~ 176ºF) at 25ºC (77ºF) ambient, for a 30-minute SSB voice transmission or a 5- to 10-minute “key-down” CW transmission at rated output. These are minimal duty cycle values for an amplifier operating in average amateur service. Longer “key-down” intervals, necessitating larger heat-dissipating surfaces and greater air circulation, are required for contest operation or at high ambient temperatures. 73 Bob, K4TAX On 1/21/2016 8:44 AM, efortner wrote: > I would like to know what the continous keydown power output rating is. The > manual talks about ICAS. I know when I get on RTTY I does not take long for > The fans to come up to full speed running 300 watts. > > Earl, K4Kay > > -----Original Message----- > From: Elecraft [mailto:[hidden email]] On Behalf Of Nand > Kishore > Sent: Thursday, January 21, 2016 4:29 AM > To: elecraft > Subject: [Elecraft] KPA500 finals blown > > KPA500 shut off with a bang while operating RTTY @300W. > > Antenna is a steppir beam. > > On opening the KPA500,found 2 ceramic? caps of VRF2933 > adrift with underside of the said caps,black. > > Have written to support.Is this the first time this has happened > in a KPA500? > > 73 and HNY, > Nandu > VU2NKS > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Bob McGraw - K4TAX
The finals could handle it, just as they handle full-carrier modes like RTTY and FM. The bigger problem, specifically described in the article, is the power supply. Many operators who use SSB or CW only, not full-carrier modes, are using power supplies that are barely adequate. They can handle 20+ amps at light duty cycle, but not CESSB, etc.
As I mentioned previously, both the K3/K3S and KX3 have excellent speech compression already, and the difference between a fairly aggressive compression setting and CESSB is, in practice, rarely going to make a difference. That said, we will be playing with this in DSP code to see if it's worth the trouble. Wayne N6KR On Jan 21, 2016, at 6:56 AM, Bob McGraw K4TAX <[hidden email]> wrote: > The recent article in February QST describing the CESSB mode is of interest. Just wondering if that mode can or will be added to the code operating the K3S? Also, wondering if the higher duty cycle of the CESSB mode will exceed the ratings of the PA stage and that of the KPA500? From what I read it seems that most SSB rated amps, past and present, may have inadequate ratings for the higher duty cycle. > > Thoughts? > > 73 > Bob, K4TAX ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Bob McGraw - K4TAX
Hi Bob,
It was an interesting article as are the QEX articles by the same author. That QST article concludes that the RF amplifier likely won't be +thermally+ strained by the CESSB, as if means that amplifier stages are operating further towards the higher efficiency point. Normal SSB has lower average power but may as a result have increased dissipation because class AB RF amplifier efficiency drops at lower power. However the author points out that +power supplies+ may well be strained by CESSB as average current will increase. Where you have an external PSU for your K3S it might not be a problem, but it may be with the KPA500 I suppose. I can't speak for Elecraft and the K3(S), but in a recent email on the subject of possibly adding CESSB to the KX3, Wayne said they will look into it. No discussion was started about the K3 or K3S on this though, but you have asked, so perhaps we might get a hint on that too. 73 from David GM4JJJ > On 21 Jan 2016, at 14:56, Bob McGraw K4TAX <[hidden email]> wrote: > > The recent article in February QST describing the CESSB mode is of interest. Just wondering if that mode can or will be added to the code operating the K3S? Also, wondering if the higher duty cycle of the CESSB mode will exceed the ratings of the PA stage and that of the KPA500? From what I read it seems that most SSB rated amps, past and present, may have inadequate ratings for the higher duty cycle. > > Thoughts? > > 73 > Bob, K4TAX > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by efortner
This in the specs in the KPA500 manual "Duty Cycle
at 500 Watts 10 minutes key down / 5 minutes standby" seems pretty definitive for normal operations, even RTTY, Earl. 73, Phil W7OX On 1/21/16 6:44 AM, efortner wrote: > I would like to know what the continous keydown power output rating is. The > manual talks about ICAS. I know when I get on RTTY I does not take long for > The fans to come up to full speed running 300 watts. > > Earl, K4Kay > > -----Original Message----- > From: Elecraft [mailto:[hidden email]] On Behalf Of Nand > Kishore > Sent: Thursday, January 21, 2016 4:29 AM > To: elecraft > Subject: [Elecraft] KPA500 finals blown > > KPA500 shut off with a bang while operating RTTY @300W. > > Antenna is a steppir beam. > > On opening the KPA500,found 2 ceramic? caps of VRF2933 > adrift with underside of the said caps,black. > > Have written to support.Is this the first time this has happened > in a KPA500? > > 73 and HNY, > Nandu > VU2NKS ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In discussions with Elecraft at Dayton, we should be able to run the KPA500
at 300 watts during a RTTY contest. This would include Running versus S/P. The fans on mine do come on high and I keep an eye on the temp reading. I do need to stop occasionally to allow the amp to cool down. I am not sure if there is a way to add an addition external fan to increase the air flow? Irwin KD3TB On Thursday, January 21, 2016, Phil Wheeler <[hidden email]> wrote: > This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10 minutes > key down / 5 minutes standby" seems pretty definitive for normal > operations, even RTTY, Earl. > > 73, Phil W7OX > > On 1/21/16 6:44 AM, efortner wrote: > >> I would like to know what the continous keydown power output rating is. >> The >> manual talks about ICAS. I know when I get on RTTY I does not take long >> for >> The fans to come up to full speed running 300 watts. >> >> Earl, K4Kay >> >> -----Original Message----- >> From: Elecraft [mailto:[hidden email]] On Behalf Of >> Nand >> Kishore >> Sent: Thursday, January 21, 2016 4:29 AM >> To: elecraft >> Subject: [Elecraft] KPA500 finals blown >> >> KPA500 shut off with a bang while operating RTTY @300W. >> >> Antenna is a steppir beam. >> >> On opening the KPA500,found 2 ceramic? caps of VRF2933 >> adrift with underside of the said caps,black. >> >> Have written to support.Is this the first time this has happened >> in a KPA500? >> >> 73 and HNY, >> Nandu >> VU2NKS >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > -- Irwin KD3TB ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Irwin, There's an easy modification you could do that might net 4-5c reduction in temperature. On the top of the amp install an additional matching fan blowing *in* through the intake. One could conceivably wire it to the fan power on the amp (though I would check what max draw is for that circuit). This will increase the air velocity, turbulence, and the CFM of the entire cooling chain. Learned this little trick working with computer water cooling. Was trying to keep a 220w TDP processor below 50c under load. If you can't get more surface area on a heat sink or radiator- increasing CFM and air turbulence can make a big difference. Michael KD8TUT On 1/21/2016 11:26 AM, Irwin Darack wrote: > In discussions with Elecraft at Dayton, we should be able to run the KPA500 > at 300 watts during a RTTY contest. This would include Running versus S/P. > The fans on mine do come on high and I keep an eye on the temp reading. I > do need to stop occasionally to allow the amp to cool down. I am not sure > if there is a way to add an addition external fan to increase the air flow? > > Irwin KD3TB > > On Thursday, January 21, 2016, Phil Wheeler <[hidden email]> wrote: > >> This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10 minutes >> key down / 5 minutes standby" seems pretty definitive for normal >> operations, even RTTY, Earl. >> >> 73, Phil W7OX >> >> On 1/21/16 6:44 AM, efortner wrote: >> >>> I would like to know what the continous keydown power output rating is. >>> The >>> manual talks about ICAS. I know when I get on RTTY I does not take long >>> for >>> The fans to come up to full speed running 300 watts. >>> >>> Earl, K4Kay >>> >>> -----Original Message----- >>> From: Elecraft [mailto:[hidden email]] On Behalf Of >>> Nand >>> Kishore >>> Sent: Thursday, January 21, 2016 4:29 AM >>> To: elecraft >>> Subject: [Elecraft] KPA500 finals blown >>> >>> KPA500 shut off with a bang while operating RTTY @300W. >>> >>> Antenna is a steppir beam. >>> >>> On opening the KPA500,found 2 ceramic? caps of VRF2933 >>> adrift with underside of the said caps,black. >>> >>> Have written to support.Is this the first time this has happened >>> in a KPA500? >>> >>> 73 and HNY, >>> Nandu >>> VU2NKS >>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [hidden email] >> > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Irwin KD3TB
Thermal design and supplementation of existing designs is not often a
trivial task. To do it properly, requires a well-reasoned, step-by-step plan that is both scientifically and mathematically driven AND limited. One cannot break the laws of physics... you can sometimes appear to bend them, but you can't break 'em. And on a fine piece of equipment like the KPA500, it would be all but criminal NOT to do it right. I've not had the privilege to see the inside of one yet, but I do have a great deal of experience solving thermal control problems. Contact me offline if you're serious about this AND you have verified that the amp is 100% operational and performing within specs. Thermal design is not a band-aid for ailing equipment. 73, ______________________ Clay Autery On 1/21/2016 10:26 AM, Irwin Darack wrote: > I am not sure > if there is a way to add an addition external fan to increase the air flow? ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Michael Cozzi
Not a bad tip... Additionally, IF you make sure your input fan has some
sort of filtering device on it, AND that as filtered produces 25%+ more CFM than the exhaust fan, you will have a VERY slightly positive pressured chassis which will assist in keeping the internals dust and dirt free. Don't make the mistake of just increasing the flow rate of an exhaust fan... Might help, but it will cause a slightly NEGATIVE internal pressure which will overrun the intake vents and start sucking all manner of grunge into the machine via every available crack and crevice... jacks, USB ports, chassis edges, etc. The less dirt inside, especially on heat sinks, the better. But again... first step is to make SURE the unit is healthy and performing within specs. 73, ______________________ Clay Autery On 1/21/2016 11:13 AM, Michael Cozzi wrote: > On the top of the amp install an additional matching fan blowing *in* > through the intake. One could conceivably wire it to the fan power on > the amp (though I would check what max draw is for that circuit). This > will increase the air velocity, turbulence, and the CFM of the entire > cooling chain. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Phil Wheeler-2
Well ... it says that, in any 15 minute interval, you can be key-down
continuously for 10 minutes followed by key-up for 5 minutes which looks like a 0.66 duty cycle on my slide rule. Presumably, this could be followed by another such sequence. Is 10 min down/5 min up repeatedly the same as 40 sec down/20 sec up repeatedly? Intuitively, it seems to me that the PA-heatsink will come to some equilibrium temp and a 10m D/5m U duty cycle may not yield the same final temp as a 60s D/20s U duty cycle. Then again, I struggled through Thermodynamics. I know the original KPA500 field testers were encouraged to run the amp at "full bars." 73, Fred K6DGW - Northern California Contest Club - CU in the Cal QSO Party 1-2 Oct 2016 - www.cqp.org On 1/21/2016 7:53 AM, Phil Wheeler wrote: > This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10 > minutes key down / 5 minutes standby" seems pretty definitive for normal > operations, even RTTY, Earl. > > 73, Phil W7OX ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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I've run echo tests on 6m EME for hours at a time which is 50% duty cycle
and 500w+. I always run RTTY contests at 500+. Yes the fans get going. That's what they're supposed to do. But I've never had a problem. 73 jim ab3cv On Thu, Jan 21, 2016 at 1:12 PM, Fred Jensen <[hidden email]> wrote: > Well ... it says that, in any 15 minute interval, you can be key-down > continuously for 10 minutes followed by key-up for 5 minutes which looks > like a 0.66 duty cycle on my slide rule. Presumably, this could be > followed by another such sequence. > > Is 10 min down/5 min up repeatedly the same as 40 sec down/20 sec up > repeatedly? Intuitively, it seems to me that the PA-heatsink will come to > some equilibrium temp and a 10m D/5m U duty cycle may not yield the same > final temp as a 60s D/20s U duty cycle. Then again, I struggled through > Thermodynamics. > > I know the original KPA500 field testers were encouraged to run the amp at > "full bars." > > 73, > > Fred K6DGW > - Northern California Contest Club > - CU in the Cal QSO Party 1-2 Oct 2016 > - www.cqp.org > > On 1/21/2016 7:53 AM, Phil Wheeler wrote: > >> This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10 >> minutes key down / 5 minutes standby" seems pretty definitive for normal >> operations, even RTTY, Earl. >> >> 73, Phil W7OX >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by wayne burdick
> That said, we will be playing with this in DSP code to see if it's > worth the trouble. In theory it should be worth the trouble as the distortion (other than any increased background noise) should be less than typical "hard" clipping with a non-phase equalized filter (for the K3, that's the KFL3B-2.7 or KFL3B-2.8). Put another way, the user should be able to clip "harder" with less distortion using the CESSB algorithm. 73, ... Joe, W4TV On 1/21/2016 10:39 AM, Wayne Burdick wrote: > The finals could handle it, just as they handle full-carrier modes > like RTTY and FM. The bigger problem, specifically described in the > article, is the power supply. Many operators who use SSB or CW only, > not full-carrier modes, are using power supplies that are barely > adequate. They can handle 20+ amps at light duty cycle, but not > CESSB, etc. > > As I mentioned previously, both the K3/K3S and KX3 have excellent > speech compression already, and the difference between a fairly > aggressive compression setting and CESSB is, in practice, rarely > going to make a difference. That said, we will be playing with this > in DSP code to see if it's worth the trouble. > > Wayne N6KR > > > > On Jan 21, 2016, at 6:56 AM, Bob McGraw K4TAX <[hidden email]> > wrote: > >> The recent article in February QST describing the CESSB mode is of >> interest. Just wondering if that mode can or will be added to the >> code operating the K3S? Also, wondering if the higher duty cycle >> of the CESSB mode will exceed the ratings of the PA stage and that >> of the KPA500? From what I read it seems that most SSB rated amps, >> past and present, may have inadequate ratings for the higher duty >> cycle. >> >> Thoughts? >> >> 73 Bob, K4TAX > > > > ______________________________________________________________ > Elecraft mailing list Home: > http://mailman.qth.net/mailman/listinfo/elecraft Help: > http://mailman.qth.net/mmfaq.htm Post: > mailto:[hidden email] Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Jim AB3CV
The KPA500 will automatically go into standby if it feels it is getting too hot.
This is done with a safety margin between that temperature and the max operating temp for the PA's. Its perfectly OK to operate it at the full fan speed. We expect it to go there in normal higher duty cycle operation. 73, Eric /elecraft.com/ On 1/21/2016 10:20 AM, Jim Miller wrote: > I've run echo tests on 6m EME for hours at a time which is 50% duty cycle > and 500w+. > > I always run RTTY contests at 500+. > > Yes the fans get going. That's what they're supposed to do. But I've never > had a problem. > > 73 > > jim ab3cv > > > > On Thu, Jan 21, 2016 at 1:12 PM, Fred Jensen <[hidden email]> wrote: > >> Well ... it says that, in any 15 minute interval, you can be key-down >> continuously for 10 minutes followed by key-up for 5 minutes which looks >> like a 0.66 duty cycle on my slide rule. Presumably, this could be >> followed by another such sequence. >> >> Is 10 min down/5 min up repeatedly the same as 40 sec down/20 sec up >> repeatedly? Intuitively, it seems to me that the PA-heatsink will come to >> some equilibrium temp and a 10m D/5m U duty cycle may not yield the same >> final temp as a 60s D/20s U duty cycle. Then again, I struggled through >> Thermodynamics. >> >> I know the original KPA500 field testers were encouraged to run the amp at >> "full bars." >> >> 73, >> >> Fred K6DGW >> - Northern California Contest Club >> - CU in the Cal QSO Party 1-2 Oct 2016 >> - www.cqp.org >> >> On 1/21/2016 7:53 AM, Phil Wheeler wrote: >> >>> This in the specs in the KPA500 manual "Duty Cycle at 500 Watts 10 >>> minutes key down / 5 minutes standby" seems pretty definitive for normal >>> operations, even RTTY, Earl. >>> >>> 73, Phil W7OX >>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [hidden email] >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Irwin KD3TB
Holy smokes. If the ceramic was actually blown off of the transistor packages (!), be careful not to inhale any ceramic dust that may be present. That's beryllium oxide which is quite toxic in dust form.
Al W6LX ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Hi,
I had thought the use of beryllium oxide had been discontinued as the insulator for RF power transistors, but no such luck: Here is the safety note from Microsemi's data sheet: "HAZARDOUS MATERIAL WARNING: The ceramic portion of the device below the lead plane is beryllium oxide. Beryllium oxide dust is highly toxic when inhaled. Care must be taken during handling and mounting to avoid damage to this area. These devices must never be thrown away with general industrial or domestic waste. BeO substrate weight: 0.703g. Percentage of total module weight which is BeO: 9%." AB2TC - Knut
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In reply to this post by Irwin KD3TB
On Thu, 21 Jan 2016 11:26:27 -0500, Irwin Darack wrote:
> The fans on mine do come on high and I keep an eye on the temp reading. I > do need to stop occasionally to allow the amp to cool down. I am not sure > if there is a way to add an addition external fan to increase the air flow? I don't have any comparison between mine and others. However, I can offer a few points about how mine runs. I use the amp at pretty much full power for meteor scatter modes (digital) on six meters daily. I have found two things. First, temperature does depend on the antenna. Even though the VSWR on the KPA indicates 1.0 for all directions that I point the antenna, the heat is higher in some directions than others. You can bet that higher SWR will cause the fan to run more than a perfect match. Second, if I keep the transmit/receive sequences down to 15 seconds each (JT9g or h, JTMSK, ISCAT), I rarely hit fan speed 5. It cycles as high as 4 every cycle after initial warm up. These on and off cycles (50% duty cycle) can continue for from a few minutes to an hour or more for one completed QSO with only an occasional excursion to fan speed 5. When I point to the southeast, the fan steps on up to speed 5 almost every other transmission period. On some modes that have longer transmit cycles, like FSK 441 with ~45 seconds on and one minute off, the fan regularly steps up to 6 after the initial few cycles. Step 6 always comes into play for me during those longer transmissions on six meters. I've found that I can reduce the heat cycle a little (noticeably) by using a small fan 2-3 feet away on the right side, blowing at the hot spot on the right rear side of the cover (this is the side panel, not the rear panel). It doesn't take much air, but it does reduce the high speed cycles. All of this is on six meters. Six meters generates more heat than HF. I never come above speed 4 (usually 3 at the most) on ten meters and below. Just because I like to be conservative and strongly dislike heat in solid state devices, I typically manually put the fan on speed 4 when I start a digital exchange and back to NORmal when done. That alone, keeps it from hitting speed 5 most of the time. Drive power for all of this is 27 watts from my xcvr (at least that's what it is set at and is likely slightly less). Power fades to lower than 450 watts on some modes when it is hot, but that could be the xcvr. Most solid state devices fade power when they get hot. Some modes run slightly less power, but that's more a function of the audio frequencies being used for the mode and response of the radio. Anyway, that's my story, and I'm stickin' to it. :) Love my KPA! Gary - AG0N ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by k6dgw
On Thu, 21 Jan 2016 10:12:08 -0800, Fred Jensen wrote:
> I know the original KPA500 field testers were encouraged to run the amp > at "full bars." I had also heard that, and it was run on RTTY at up to 700W during a contest. Gary - AG0N ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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