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KPA100 Hi Current on 30M

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Gottlieb, Jonathan

KPA100 Hi Current on 30M

Almost finished with my KPA100. Power output is 100 watts on all bands except 30M where I get hi current display over 55 watts. Any suggestions?

Jonathan Gottlieb
WA3WDK
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Ken Wagner K3IU

RE: KPA100 Hi Current on 30M

Hi Jonathan:

You may well have joined "the group." But first...

Make sure that you can get at least 10 watts output on all bands with the
KPA100 turned "Off" in the menu. Then you should recheck the power
calibration procedure for the KPA100 unless you are very confident that it
is correct.

If both of those check out OK, then you are probably experiencing the same
thing that several others (with you I think there are now 9) that are having
pretty much the same problem. Elecraft and the designer are working on the
problem and I'm sure there will be a solution soon. In the meantime, one of
the things that has worked for some is to increase the capacitance at C80
and C81 between T1 and the bases of the PA transistor. Some have changed to
5600 pF, some have added another 4700 pF, and I ended up adding 2200 pF. One
ham in England who had the problem replaced C80 and C81 with new 4700 pF
caps from Elecraft and the problem remained. He then purchased locally and
installed replacement new metal film resistors to replace R19 and R20 and
new 4700 pF caps to replace C80 and C81 and the problem was completely
resolved for him. It suggests that the provided resistors may have enough
inductance to resonate with the 4700 pF cap and create a "trap" at around 10
MHz.

I encourage you to report the problem to Gary <[hidden email]> so that
they are aware that there is another builder with this problem.

73,

Ken K3IU

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Gottlieb, Jonathan
Sent: Sunday, June 12, 2005 12:12 PM
To: [hidden email]
Subject: [Elecraft] KPA100 Hi Current on 30M

Almost finished with my KPA100. Power output is 100 watts on all bands
except 30M where I get hi current display over 55 watts. Any suggestions?

Jonathan Gottlieb
WA3WDK

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James T. "Jim" Rogers, W4ATK

RE: KPA100 Hi Current on 30M

In reply to this post by Gottlieb, Jonathan

I am a bit mystified by the reports of low power on 30M. I have K2 #4028
and bought my KPA-100 at the time I purchased my K2. Barefoot on 30M, I have
15w out (measured) and QRO a good solid 100W (measured). If I choose to
observe power out in TUNE, the K2 will cut the power to around 55W, but
coming out of tune and closing the key will get me a good solid 100W. I have
not experienced a problem with overcurrent. I wonder what has changed in the
more recently delivered KPA100s to cause the problem?

Just for grins, I switched in the dummy load and on 30M with the POWER
control at full throttle, I can bump 3.5 amps according to the K2 current
display. And as reported above, a rock solid 100W.

Just curious.

Jim, W4ATK
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Ken Wagner K3IU

RE: KPA100 Hi Current on 30M

Hi Jim:
Looks to me like your KPA100 is working just fine. When I press "Tune" the
power on mine gets reduced to 20 watts so long as the power commanded is
greater than 20 watts. I just checked it with the output going directly to
a dummy load and with the KAT100 disconnected. If you first tap the Display
button to show volts and amps, then pressing the "Tune" button will produce
the commanded power out and not be limited to 20 watts. I have no idea why
you are getting the 55 watts when you press Tune <g>
73, Ken K3IU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At 02:49 PM 6/12/2005, James T. \"Jim\" Rogers, W4ATK wrote:

> I am a bit mystified by the reports of low power on 30M. I have
> K2 #4028
>and bought my KPA-100 at the time I purchased my K2. Barefoot on 30M, I have
>15w out (measured) and QRO a good solid 100W (measured). If I choose to
>observe power out in TUNE, the K2 will cut the power to around 55W, but
>coming out of tune and closing the key will get me a good solid 100W. I have
>not experienced a problem with overcurrent. I wonder what has changed in the
>more recently delivered KPA100s to cause the problem?
>
> Just for grins, I switched in the dummy load and on 30M with the
> POWER
>control at full throttle, I can bump 3.5 amps according to the K2 current
>display. And as reported above, a rock solid 100W.
>
>Just curious.
>
>Jim, W4ATK

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Robert Fanfant

Re: KPA100 Hi Current on 30M

In reply to this post by Ken Wagner K3IU

Is this a problem only on 30M?
-rob N7QT

----- Original Message -----
From: "Ken K3IU" <[hidden email]>
To: "'Gottlieb, Jonathan'" <[hidden email]>; <[hidden email]>
Sent: Sunday, June 12, 2005 11:29 AM
Subject: RE: [Elecraft] KPA100 Hi Current on 30M

> Hi Jonathan:
>
> You may well have joined "the group." But first...
>
> Make sure that you can get at least 10 watts output on all bands with the
> KPA100 turned "Off" in the menu. Then you should recheck the power
> calibration procedure for the KPA100 unless you are very confident that it
> is correct.
>
> If both of those check out OK, then you are probably experiencing the same
> thing that several others (with you I think there are now 9) that are
> having
> pretty much the same problem. Elecraft and the designer are working on the
> problem and I'm sure there will be a solution soon. In the meantime, one
> of
> the things that has worked for some is to increase the capacitance at C80
> and C81 between T1 and the bases of the PA transistor. Some have changed
> to
> 5600 pF, some have added another 4700 pF, and I ended up adding 2200 pF.
> One
> ham in England who had the problem replaced C80 and C81 with new 4700 pF
> caps from Elecraft and the problem remained. He then purchased locally and
> installed replacement new metal film resistors to replace R19 and R20 and
> new 4700 pF caps to replace C80 and C81 and the problem was completely
> resolved for him. It suggests that the provided resistors may have enough
> inductance to resonate with the 4700 pF cap and create a "trap" at around
> 10
> MHz.
>
> I encourage you to report the problem to Gary <[hidden email]> so
> that
> they are aware that there is another builder with this problem.
>
> 73,
>
> Ken K3IU
>
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Gottlieb, Jonathan
> Sent: Sunday, June 12, 2005 12:12 PM
> To: [hidden email]
> Subject: [Elecraft] KPA100 Hi Current on 30M
>
> Almost finished with my KPA100. Power output is 100 watts on all bands
> except 30M where I get hi current display over 55 watts. Any suggestions?
>
> Jonathan Gottlieb
> WA3WDK
>
> _______________________________________________
> 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