[Elecraft] K3 strange overshoot

[Michael Tope]

Hi Tony,

I've noticed that whenever I adjust the drive on the K3 either up or 
down, there is an initial power overshoot on the first dit after the 
adjustment. I use an Alpha 87A which can be sensitive to drive 
(sometimes the overshoot causes a grid over-current fault), so I've 
gotten into the habit of putting it in standby after a drive adjustment 
on the K3. Then, I send a dit, after which I put the Alpha 87A back into 
operate mode. I thought this was an design idiosyncrasy I had to live 
with. I'll have to give the re-calibration procedure you describe a try 
to see if that fixes the problem.

Thanks,

73, Mike W4EF....................

On 2/21/2022 12:49 PM, N2TK via Elecraft wrote:
> I got way behind with my personal email so not sure if there has been 
> follow-up to this.
> I have a K3/KPA1500. A final in the KPA1500 blew and took out the K3 
> too. Both went back to Elecraft for repair. This was the third trip 
> back for the KPA1500.I was told the log showed over drive on the amp. 
> This was very puzzling as I never drove the amp hard, at least not to 
> my knowledge. I was concerned about using it. Thought about selling it 
> as it was fresh back from the factory again and checked out. But not 
> sure if there was an inherent problem with the amp so didn't want to 
> pass this on to someone else. When it came back I left it in the box 
> for quite a while. Used the KPA500 instead. Finally set it up for 
> ARRLDXCW. But kept my drive at <20W. My amps are in the basement on a 
> shelf literary right below my feet where I sit to operate. My left 
> monitor is off about 45 degrees. This is where I have a window for the 
> KPA1500 Remote screen window. What I noticed, even with <20W drive, 
> when I changed any bands, the first key shot the power way up. After 
> the first keying the power dropped down to what you would expect. Any 
> keying after that would be fine until I changed bands. Maybe this is 
> why the KPA1500 finals died?
> I was told this is caused by the K3. If you set the K3 to exactly 5 or 
> 50W the calibration will change and cause this spike. Someone told me 
> to do a recalibrate on the K3 (sorry I don't remember who told me to 
> do that? This K3 had come back from Elecraft along with the KPA1500.I 
> did that and guess what, the spike on the KPA1500 went away even when 
> changing bands. Since I did this I make sure the K3 is never set up 
> for either 5 or 50w. Everything worked fine all weekend, but with 
> reduced power. I was eagle eye when changing bands and so far have not 
> seen the problem come back.
> Is this K3 issue about the problem happening if you set up and 
> transmit with the K3 at 5W or 50W for real? Is it widespread? I have 
> to assume Elecraft isn't aware of this, if it is a real problem. I got 
> to assume they would have sent out a notice or a possible software 
> upgrade to fix this.
> Bob, no idea if this is the overshoot problem you are seeing.
> By the way, what drive power are folks using to get 1500W out of the 
> KPA1500?Also, I don't believe the SWR has had any involvement with 
> this problem. All my antennas SWR are below <1.5.
> 73,N2TK, Tony
>
>
> -----Original Message-----
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: elecraft at mailman.qth.net
> Sent: Fri, Feb 11, 2022 5:34 pm
> Subject: Re: [Elecraft] K3 strange overshoot
>
> On 2/11/2022 2:06 PM, Bob McGraw wrote:
>> I see a small initial overshoot when changing bands. Drive power for
>> each band is different.
> Same here. I think it's the K3, and I think it's normal.
>
> 73, Jim K9YC