[Elecraft] Strange KPA100 behavior

[Mike Geddes]

Don,

This evening I have had a chance to look at my KPA100 again.  I verified 
that I am still unable to control output above 11 watts . . . .  above 11 
watss it is putting out 165 watts (connected to Bird 43 meter) and showing 
7:1 SWR on K2 display.  Below 11 watts the output seems correct. I was 
incorrect in an earlier email.

I DO have blue toroids at L16 and RFC1, and L15 is empty.  I did verify that 
C31 is .22mF (m22J63).

I checked T4 . . . looks okay and I seem to have proper resistance between 
1/3 and 2/4. And I do have continuity between 1/4.

One curious observation . . . as I was working through the check and 
alignment process again, I can only get 26.5k and 27.1k out of R26 and R27, 
versus the 43k recommended for C1 adjustment.

Not sure what to look at from this point?  Sorry for the prior 
misinformation.  Any suggestions?

Thanks,

Mike
N4JX

----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at earthlink.net>
To: "Mike Geddes" <geddes at tampabay.rr.com>
Cc: "Elecraft" <elecraft at mailman.qth.net>
Sent: Monday, June 11, 2007 8:56 AM
Subject: Re: [Elecraft] Strange KPA100 behavior


> Mike,
>
> Is the K2 displaying 165 watts?  Or is the K2 displaying 0.2 watts or 
> lower while an external wattmeter is displaying 165 watts?
> What is your test setup that gives you a 7:1 SWR?  If you are feeding a 
> resistive 50 ohm dummy load with good coax, the wattmeter (either internal 
> or external) should read 1:1 even with a KPA100 problem.
>
> Tell us more so we can help with your problem -
> Taking a very wild guess, you either have a non-functioning wattmeter in 
> the KPA100, or the KPA100 wattmeter is not calibrated, or you have a 
> parasitic oscillation in the KPA100.
>
> Since this is a new kit - do you have blue toroid cores at L16 and RFC1 or 
> do you have red toroids at L15 and L16?  And tell us what the value of C31 
> is and whether you determined the value by looking at the capacitor 
> (preferred) or whether you just looked at the parts list/schematic.
>
> We need the answers to all these questions before we can advise you 
> further.
>
> 73,
> Don W3FPR
>
> Mike Geddes wrote:
>> Greetings. I recently finished my K2 KPA100 kit. It seemed to work okay 
>> initially, then last night started to exhibit some strange behavior.  It 
>> would transmit correct power on tune under 11 watts (and show low SWR), 
>> but on anything over 11 watts, on tune, it would transmit around 165 
>> watts and show an SWR of around 7:1!!  And giving High Current message Is 
>> there anything I should start looking for initially?
>>
>> Any suggestions are appreciated.
>>
>> Thanks,
>> Mike
>> N4JX
>