[Elecraft] KPA100 oscillation during IARU Reg 1 Field Day

[w6jd at comcast.net]

I  wonder if Jukka remembered to re-tighten the screws holding the transistors to the heat sink after the first 10 hour "break in" period?

Doug
W6JD

-------------- Original message -------------- 
From: "Stephen W. Kercel" <kercel1 at suscom-maine.net> 

> Fellow Elecrafters: 
> 
> I've had my K2 for only a short while, and I find that Jukka rises a 
> point that I've been wondering about. Can the K2 transmit at 100 
> Watts (into low SWR) CW (say 20-30 wpm) in a continuous session for 
> tens of hours on end without damage? 
> 
> I usually use my rig in QRP mode, and only occasionally go to 100 W. 
> It always bothers me when the fan comes on even though I realize that 
> it is normal and desirable behavior. Thus far, I've only made one or 
> two extended "rag chew" QSOs where I've made long CW transmissions at 
> full power. 
> 
> Consequently, I have not much feel for how the rig should work while 
> transmitting CW at full power for extended periods of time. (As we 
> see from Jukka's post, running the rig until one smells smoke is not 
> a good idea.) What is a reasonable operational cycle? What is the 
> line between acceptable operation and abuse? 
> 
> Any insight from experienced K2 QRO operators would be most welcome. 
> 
> 73, 
> 
> Steve 
> AA4AK 
> 
> 
> 
> 
> At 04:21 AM 6/5/2006, Jukka Tarvainen wrote: 
> >Hello! 
> > 
> >Sunday afternoon my KPA100 started oscillating, I believe. It happened just 
> >when heavy rainshower hit our site. I was using a Spiderbeam on 20 meters 
> >and running small CW pileup with 100 watts. Rig was performing well for 18 
> >hours on various bands and it was running quite hot. I put fan running high 
> >continuously in the beginning of contest. 
> > 
> >When this happened I disconnected power supply. K2 seem to work normally 
> >when KPA100 is not active. When KPA comes on it shows "Hi refl" immediately 
> >when transmitting and draws 20-30 amps from 30 amp power supply. Power 
> >supply starts to limit and cuts power. 
> > 
> >There was some smoke smell coming from K2. Can't see any blown away parts. 
> >Couple of 2 and 3 watts resistors have been warm, they are bit brownish. Any 
> >ideas what and where to start looking for? I built my K2 and options, but 
> >I'm technically challenged :) 
> > 
> >Jukka Tarvainen, OH4MFA 
> >K2/100 #4293 
> >oh4mfa at sral.fi 
> >http://personal.inet.fi/koti/oh4mfa 
> > 
> > 
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