[Elecraft] K3 erratic power output

[GW0ETF]

k7ca wrote:
> 
> Hello All,
>   I just received K3 kit serial # 1253 with KPA3, KBPF3, KXV3 and 
> KUSB options.  The kit was very well thought out and was a pleasure 
> to assemble.  It went together in under 8 hours.  Everything 
> seemed to calibrate well and work perfectly except for the 100 watt 
> PA.  When running 12 watts or less (8 watts on 6m) output is good and 
>  stable.  When power is set higher which causes the 100 W PA to turn 
> on, output power is not stable.  On 20m thru 6m with key down the  
> power output takes about 6 or 7 seconds to stablize.  For example, 
> when the power control is set for 50 watts it first comes up to 35 
> watts, then slowly goes up to 60 or 70 watts, then slowly comes down 
> to 50 watts where is is stable.  It seems like the power control 
> zero's in on the correct power but very slowly.  With CW it never 
> gets there. This happens every time the key is opened and then closed 
>  again.  On 40m the same thing happens but there is about a 3 second 
> delay after key closure before any output is seen.  There is no power 
>  output at all on 80m and 160m even though with less than 12 watts 
> set on the power control there is normal power output. I haven't had 
> the time to look into the schematic yet so thought I'd see if any of 
> the list readers have had a similar experience or may have some idea 
> of a good place to start.    Thanks, Al K7CA
> 
> 

Al,

There have been posts previously about erratic power output but maybe not
describing such an extreme situation as yours - no output (high) at all on
some bands suggests something more serious than erratic power control....:-(

I have occasionally found the power output to suddenly start changing (CW)
but it has happened only rarely and never sure if it is connected to a
software upgrade or not. Mostly it manifests in the power indication
dropping from the '100 watt' level to anything from 35 watts to 80 but it
always seems to recover quickly; it is a genuine power variation as checked
against an external power meter. Once when I was using my amp it went the
other way and increased up towards full power which meant I was briefly
knocking out about 1200 watts - I wondered whether Elecraft would bail me
out if a man in a grey suit came knocking complaining about me operating
outside my licence conditions...:-)

It happened again fairly recently and I went back to the last full firmware
version (2.02 I think....) and I've not noticed it since. I'm not convinced
though that it is linked to software but I've not even thought about
hardware yet 'cos I'm waiting for a KRX3 which will involve some dismantling
and checking of connections etc.

Can't be a widespread problem though in view of the dearth of posts on this
but it does seem to exist and hopefully if it is a 'real' problem compared
to dodgy contacts somewhere, it will be resolved soon. I do wonder if the
lack of reporting is because of the fact that it will be much more obvious
in CW and may well go unnoticed in ssb.

Good luck,

Stewart Rolfe, GW0ETF (K3/100 145)
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