[Elecraft] Strange KPA100 behavior

[geddes at tampabay.rr.com]

Don,

I am not at home right now to look at K2, but will try and answer your 
questions to provide additional information.

I am not sure what the K2 was displaying in terms of watts out (I 
think it was a low number), but I confirmed the output at 165w using 
two external wattmeters (first the Elecraft W1, which I did not 
totally believe because it was maxed out, then my Bird 43 with 1000w 
slug).  I was connected to a Bird 125w dummy load, confirmed 50 ohm. 
The cable was probably not the best, it was a 20 ft run of RG-58 I 
think.

My kit used the red toroids, and I assume at L15 and L16 but would 
have to check when I can look at the kit (when I get home). Also will 
have to check the value of C31.  

Don't know if this will help you or not . . but this is what I can 
provide for now.  Will check the rest when I get home this evening.

Thanks,

Mike
N4JX


----- Original Message -----
From: Don Wilhelm <w3fpr at earthlink.net>
Date: Monday, June 11, 2007 8:57 am
Subject: Re: [Elecraft] Strange KPA100 behavior
To: Mike Geddes <geddes at tampabay.rr.com>
Cc: Elecraft <elecraft at mailman.qth.net>

> 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
>