[Elecraft] [P3] P3 woes - repaired but now claims my K3s puts out 873W!

[Alan Bloom]

Hi Dave,

There is a "SensorCal" entry in the Transmit Monitor Menu, but I don't 
think it has enough range to correct such a large error.

There is also a "MtrScale" entry to set the full-scale power on the 
meter display.  Does the reading change when you change the scale?

In addition to the I/O board, the problem could also be on the Sensor 
board (the small board that connects the sensor RJ45 connector to the 
I/O board).  If one of the resistors on this board went open or shorted 
it could cause a power error.  Is the reverse power reading way off as 
well?  (i.e. does the SWR read wrong for SWR not close to 1:1?)  If so, 
that could be due to a resistor problem on the Sensor board.

 > I'm wondering if the new revision I/O board is somehow incompatible 
with the older TX Monitor board,

No I don't think so.  There was a minor change in the sensor design at 
one point but it was just a capacitor change to improve the detected 
bandwidth so the envelope would display correctly.  (The same sensors 
are used for the W2 wattmeter.)

73,

Alan N1AL



On 4/7/23 12:12, Dave New, N8SBE wrote:
> So, I was the guy that had a P3 display/boot problem recently.
>
> I sent it to the mother ship for repair, and they found that (get 
> this) the 12V supply was shorted to the 3.3V supply (eep!).
> So, a new(er) I/O board (which contains the supplies) and a 
> replacement blown 3.3V LCD controller later, I have an (almost) fully 
> functional P3 again.
>
> EXCEPT, the TX Monitor function is now funky.  It claims that my K3s 
> is putting out 873 (or so) watts!  I've tried both sensors (I had a 
> 200W HF sensor on the shelf since I added a KPA500 and changed to a 
> 2KW HF sensor), and although the scale max changes on the P3 display 
> when I change sensors, it still way overstates my output power.  The 
> KPA500 is showing 1360 watts on the P3!
>
> I unplugged/re-plugged everything, did a visual inspection of the TX 
> Monitor adapter board under a lighted magnifying glass, looking for 
> missing/broken SMD resistors or caps, but so far no soap.
>
> I'm wondering if the new revision I/O board is somehow incompatible 
> with the older TX Monitor board, or maybe there is a missing 1M-ohm 
> resistor to ground on the I/O board at the sensor connector, or an 
> incorrect series resistor value there.
>
> And yes, I sent a note to support, but I haven't heard back, yet. 
> Wondering if anyone (Alan?) has any ideas where this behavior is 
> coming from.  The wattmeter in both my K3s and KPA500 are working 
> normally.  It's just the P3 wattmeter that's gone off the deep end, now.
>
> Thanks, and 73,
> -- Dave, N8SBE
> ______________________________________________________________