[Elecraft] [P3] P3 woes - internal display inop

[Dave New, N8SBE]

Alan,

Moving the jumper to 1-2 doesn't change the behavior.  The internal 
display comes on briefly,
then the P3 powers down.  I've tried it in all 3 positions, and the 
behavior is the same
whenever the P3 attempts to power on.

And no, I can't contact it via the utility anymore.  The most recent 
time I did manage to contact it
was when the external display was running.  Now neither display works, 
except the internal one for
about a second or so.

I notice that the red LED on the display PCB no longer comes on, either, 
now that I have the lid off of the P3.

73,

-- Dave, N8SBE

On 2023-02-26 14:53, Alan Bloom wrote:
> By the way, I no longer have a K3 or P3 (lost in a house fire) so this
> is from memory...
> 
>> Since the internal display seems to show OK, no matter how briefly,
>> I'm thinking this is not an internal display connection issue.
> 
> Agreed.
> 
>> This seems to be a power on reset issue of some sort.
> 
> Can you send/receive RS-232 commands to the P3?  If so, then the power
> must be on.
> 
> If you haven't already, I would try moving the power-on jumper (on the
> rear-panel I/O board at the back of the P3) to the "always on"
> position (jumper pins 1 and 2).
> 
>> I take it that the 3.3V supply is 'on' as long as 12V external is 
>> supplied to the P3?
> 
> No, it's only on when the P3 is on.
> 
> What happens is that when the P3 CPU wakes up, one of the first things
> it does is to enable the PWON signal to the I/O board which holds the
> power on.  If that is not working for some reason, then moving the
> power-on jumper to "always on" should force the P3 to stay on.
> 
> Alan N1AL
> 
>