KPA100

[Brent Sutphin WB4X]

I recently built and installed a KPA100 on my K2.  It works great but today
on twenty meters I got a high current message and the amp shut down.  I have
the driver current set for 4 amps.  Any suggestions?

Brent   WB4X


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[Vic K2VCO]

Brent Sutphin WB4X wrote:
> I recently built and installed a KPA100 on my K2.  It works great but
> today on twenty meters I got a high current message and the amp shut
> down.  I have the driver current set for 4 amps.  Any suggestions?

First check the current at 10 watts (amp off).  If it's reasonable, then
you have the 'hard to drive on 20-30 meters' problem.  The last thing I
heard was that C81 and C82 in the KPA100 can be increased to 5600 pf to
help.  However, I don't fully understand this, so I suggest you ask Gary
<[hidden email]>.

If the current is high-ish at 10 watts, make sure the 20 meter bandpass
filter trimmers are not at maximum capacity.  I had to parallel some
small capacitors with them to get the adjustment within range.

What's 'normal' current?  I'm drawing about 3.2 amps on 20 meters now,
less on other bands.  This of course is with the KPA100 running 100
watts, measured by tappinf DISPLAY.

--
73
Vic, K2VCO
Fresno, CA
http://www.qsl.net/k2vco
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[Ken Wagner K3IU]

Hi Brent:

To add to what Vic said, make sure that you have the power calibration done
properly. Also, one of our British friends recently replaced the C80/C81
caps AND the R19 and R20 resistors with locally procurred 4700 pf and 1.5
Ohm 2W resistors and all of the problems went away. It is my understanding
that  the folks at Elecraft are working with the designer to sort this out.

By my count there seems to be now 7-8 instances of this problem with the
KPA100... all shipped out since about Feb/Mar time frame.

Please do let Gary know you are having this problem. I suspect that the
more folks that have it and report it, the quicker it will be resolved <g>.

73,
Ken Wagner K3IU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At 03:54 PM 6/11/2005, Vic Rosenthal wrote:

>Brent Sutphin WB4X wrote:
>>I recently built and installed a KPA100 on my K2.  It works great but
>>today on twenty meters I got a high current message and the amp shut
>>down.  I have the driver current set for 4 amps.  Any suggestions?
>
>First check the current at 10 watts (amp off).  If it's reasonable, then
>you have the 'hard to drive on 20-30 meters' problem.  The last thing I
>heard was that C81 and C82 in the KPA100 can be increased to 5600 pf to
>help.  However, I don't fully understand this, so I suggest you ask Gary
><[hidden email]>.
>
>If the current is high-ish at 10 watts, make sure the 20 meter bandpass
>filter trimmers are not at maximum capacity.  I had to parallel some small
>capacitors with them to get the adjustment within range.
>
>What's 'normal' current?  I'm drawing about 3.2 amps on 20 meters now,
>less on other bands.  This of course is with the KPA100 running 100 watts,
>measured by tappinf DISPLAY.
>
>--
>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

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