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

[Alan Bloom]

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




On 2/26/23 12:22, Dave New, N8SBE wrote:
> Alan,
>
> Before I got the chance to look into your idea of possibly bad display 
> connection,
> I DID reload a saved configuration into the P3 using the P3 Utility, 
> and it restored
> the high-res setting on the external display.
>
> After power cycling (the generator quit unexpectedly due to a low oil 
> sensor),
> now I can't get the external display on at all, but interestingly, the 
> internal
> display comes up briefly with the P3 Boot Loader and Checksum Test 
> messages, and
> if it's been a while since I've tried to power up, I get a brief 
> spectrum display
> with the message, Waiting for SVGA, then it goes blank, apparently 
> with an internal
> power fail, since every time I push the Power button, I get the same 
> sequence.
>
> Since the internal display seems to show OK, no matter how briefly, 
> I'm thinking this
> is not an internal display connection issue.
>
> This seems to be a power on reset issue of some sort.  I note from the 
> schematic that
> that Power button feeds SW_ON which is tied to INT4/A15 on the PIC33F 
> chip.  I'm assuming
> the PIC has that pin programmed for INT4, so pushing the Power button 
> is 'waking up' the PIC33F
> with INT4, and it goes partially through the start up, and then fails 
> apparently failing to
> latch 'on' from the momentary push button press.
>
> I take it that the 3.3V supply is 'on' as long as 12V external is 
> supplied to the P3?
>
> Thanks,
> -- Dave, N8SBE
>
> On 2023-02-24 13:23, Alan Bloom wrote:
>> Hi Dave,
>>
>> Another possibility is that perhaps one of the display connectors has
>> come loose or is making a bad connection.
>>
>> I normally wouldn't recommend this since these tiny connectors are
>> kind of tricky, but since the P3 isn't working anyway, there's nothing
>> to lose.
>>
>> There are two surface-mount connectors located underneath the display
>> on the front-panel board: a 4-pin connector for the display backlight
>> and a 40-pin connector for the rest of the display electronics.
>>
>> To access them, remove the front-panel board from the P3 and then
>> remove the LCD display by gently prying it free from the rubber
>> holder.  Be careful so as not to put stress on the flex circuits going
>> to the two connectors.
>>
>> Examine each of the connectors to see if it looks like the flex
>> circuits are properly seated in them.  To re-seat one, open the
>> connector by using a fingernail to pop open the top.  After
>> re-positioning the flex circuit, press the connector top down again
>> until it clicks.
>>
>> As I say, this is a rather delicate operation (which is why the front
>> panel came pre-assembled in P3 kits).  So you might want to consider
>> sending the P3 in for service and let the experienced Elecraft techs
>> handle it.
>>
>> Alan N1AL
>>
>>
>>
>> On 2/24/23 10:51, Dave New, N8SBE wrote:
>>> Mike,
>>>
>>> Thanks for the idea!  I hadn't considered that mitigation.
>>>
>>> Anyone else have ideas for a permanent corrective action?
>>>
>>> 73,
>>> -- Dave, N8SBE
>>>
>>> On 2023-02-24 09:13, Mike Flowers wrote:
>>>> Hi Dave,
>>>>
>>>> If you have a way of sending P3 control commands to the P3, there 
>>>> may be a
>>>> chance that you could the resolution of the external display set to a
>>>> useable value.
>>>>
>>>> I've attached my copy of the P3 Programmer's Reference.
>>>>
>>>> - 73 and good DX de Mike, K6MKF, NCDXC Life Member
>>>>
>>>>
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