Topics

Help ! My U3S behaves badly.... #u3s


PA3CRZ
 

Hi there,

I decided to redo my U3S casing and wiring, because the last time it was a mess. But it worked !
Powersupply-wise, I now have two 7805's that supply 5V to the oscillator and the U3S respectively.
That's the only big change I made.....

Now, when I start up the U3S I get the splash screen, and then it seems to cycle very quickly through
all available menus, before it ends saying "Press right button".
When I do that, it just starts over cycling through the menus, before stopping and displaying the same message
again, And so on......

Did a factory reset using the button on the PCB, but the behavior stays the same.

Has anyone seen this before ?
Does anyone know what could be the problem ?

FYI, I used Pete's blog https://zl2ik.blogspot.com/2015/11/u3s-beacon-kit.html for inspiration on the powersupply.
I do not have the oven, so I'm only using two 7805's.

Any help would be enormously appreciated. I'm without WSPR now, and that makes me sad.....

Kind regards and 73,
Hans
PA3CRZ


Vernon Matheson
 

Have you got a short in your left menu button

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of PA3CRZ
Sent: Tuesday, July 16, 2019 3:35 PM
To: QRPLabs@groups.io
Subject: [QRPLabs] Help ! My U3S behaves badly.... #u3s

 

Hi there,

I decided to redo my U3S casing and wiring, because the last time it was a mess. But it worked !
Powersupply-wise, I now have two 7805's that supply 5V to the oscillator and the U3S respectively.
That's the only big change I made.....

Now, when I start up the U3S I get the splash screen, and then it seems to cycle very quickly through
all available menus, before it ends saying "Press right button".
When I do that, it just starts over cycling through the menus, before stopping and displaying the same message
again, And so on......

Did a factory reset using the button on the PCB, but the behavior stays the same.

Has anyone seen this before ?
Does anyone know what could be the problem ?

FYI, I used Pete's blog https://zl2ik.blogspot.com/2015/11/u3s-beacon-kit.html for inspiration on the powersupply.
I do not have the oven, so I'm only using two 7805's.

Any help would be enormously appreciated. I'm without WSPR now, and that makes me sad.....

Kind regards and 73,
Hans
PA3CRZ


Andy Brilleaux <punkbiscuit@...>
 

On Tue, Jul 16, 2019 at 04:49 PM, Vernon Matheson wrote:
Have you got a short in your left menu button
That's what I thought.

I have also discovered that these cheap switches can misbehave if they are overtightened when attaching to a front panel.

The internals seems to get a bit distorted mechanically and misbehave/


Alan de G1FXB
 

I've seen stripped threads on 1/4" through panel potentiometers....
There is no Need to wring the living daylights out of any the mounting nut's.

Nip then up a bit tighter than finger tight and use a "locking" compound.
For hobby use easiest to obtain is from the XYL / life partner.
Nail varnish is fine.
If you need to purchase your own, you may feel a little self conscious rummaging around in the 50 pence clearance bins for the out of favour last years colours......
Just explain it's for your hobby.....

Alan

On 17/07/2019 06:28, Andy Brilleaux via Groups.Io wrote:
On Tue, Jul 16, 2019 at 04:49 PM, Vernon Matheson wrote:
Have you got a short in your left menu button
That's what I thought.

I have also discovered that these cheap switches can misbehave if they are overtightened when attaching to a front panel.

The internals seems to get a bit distorted mechanically and misbehave/


Don--AE4DW
 

S1 and S2 simply take two different pins of the processor to ground, so i would appear you have something holding pin 25 to ground all the time.

If you can't trace it out and find the issue with your modifications in place, and assuming it all worked fine before your regulator mod, then the obvious next step, as much of a pain as it is, is to undo your regulator mod and confirm (or disprove) that modification created the issue.

 


PA3CRZ
 

Thanks guys, for all the answers.

I disconnected the external buttons, and now the U3S starts up with "Diagnostic".
After pressing the button on the PCB, the splash screen appears, and I can further configure the device.
So, it does seem that the pin 25 button was shorted to ground. However, measuring the button without it
being connected to the PCB there is no shortcircuit (only when I press the button, of course......).

So, I'm still not sure why this happens.
Will investigate further. For now, the U3S is usable again. I just can't configure it using the external buttons...

Thanks, 73
Hans


Don--AE4DW
 

Glad to see you got a few steps closer to the root cause.

Could you possibly have the pin 25 lead being shorted to ground somewhere in the case (is it metal?) at the connection point to the switch? Or a strand of wire (difficult to see..) between the terminals of the switch giving you that constantly-closed state?  Not sure whether the switch is mounted in your case, or removed, but I'd be curious if you still had the issue with the button removed from the case, the two leads to the switch free and clear of anything.

It sounds like the switch is fine, but its always easy to replace it with a new one to confirm. 


PA3CRZ
 

Hi Don,

Miracles do happen from time to time....
I put it all together again, and now it's working perfectly. Didn't change anything....

It must have been something like you said, maybe a short against the metal case.
Just made sure this time that the connectors to the pins on the PCB were bent slightly more away from the
bottom of the case (although I used heat shrink, so no visible exposed connectors).
Possibly, this was the cause of the trouble.

Anyway, U3S is working fine now, and I have my first long distance report (to ZS1LS, almost 10,000 km), using only 200 mW in
 a small dipole antenna. Not the best of circumstances here, but a nice result.

Thank you, and everyone else, for the support.
On to my next project!

Regards and 73,
Hans
PA3CRZ