Latest QCX-mini pcb rev.2 and C38 mod #manual #mods #pcbversion #qcxmini #c38


john@...
 

Hello all,
I've almost completed the build of a latest batch QCX-mini.
I've followed the assembly instructions v1.05 (latest rev?) to the point where I should add the additional capacitor C38, but realised the new pcb layout v2 has a new regulator chip, and fitting the additional electrolytic as detailed would now achieve nothing, because the regulator pinout has changed and the lead of the diode and adjacent regulator pin pad are actually the same node electrically.  I could find an alternative point to earth the capacitor, e.g. the heatsink tab of the regulator, but since the regulator is now different, is it still necessary to perform the modification?
Has anyone else got this far with the latest batch of rev.2 pcbs?
It's gone well so far, I haven't spotted any other changes on the rev.2 board until now.
John G3ZTU


Hans Summers
 

Hi John

There is no need for the capacitor in Rev 2. No additional 10uF capacitor in Rev 2 (with the 78M05 regulator). I have not yet been able to update the manual.

The only changes to the Rev 2 PCB are the change of voltage regulator to 78M05; and moving some components in the immediate area to make space for it (as 78M05 is larger than AMS1117). 

73 Hans G0UPL
http://qrp-labs.com

On Fri, Feb 19, 2021 at 2:48 PM <john@...> wrote:
Hello all,
I've almost completed the build of a latest batch QCX-mini.
I've followed the assembly instructions v1.05 (latest rev?) to the point where I should add the additional capacitor C38, but realised the new pcb layout v2 has a new regulator chip, and fitting the additional electrolytic as detailed would now achieve nothing, because the regulator pinout has changed and the lead of the diode and adjacent regulator pin pad are actually the same node electrically.  I could find an alternative point to earth the capacitor, e.g. the heatsink tab of the regulator, but since the regulator is now different, is it still necessary to perform the modification?
Has anyone else got this far with the latest batch of rev.2 pcbs?
It's gone well so far, I haven't spotted any other changes on the rev.2 board until now.
John G3ZTU


john@...
 

Hi Hans,
that was quick!  Thanks for getting back, saves me a fiddly job.
Others reaching the same point may see this thread and know they can skip the mod.
I've enjoyed the build, now girding my loins for the smoke test!
All the best, and thank you!
John
G3ZTU


Hans Summers
 

Hi John

Whatever smokes, it won't be that regulator :-D 

And remember, all Rev 2 boards have been through my super-duper test jig and passed its 21 tests. All 1,000 boards. Yes the test jig really did survive that beating!

73 Hans G0UPL

On Fri, Feb 19, 2021 at 3:04 PM <john@...> wrote:
Hi Hans,
that was quick!  Thanks for getting back, saves me a fiddly job.
Others reaching the same point may see this thread and know they can skip the mod.
I've enjoyed the build, now girding my loins for the smoke test!
All the best, and thank you!
John
G3ZTU


jmh6@...
 

Hi All :),

WOW! I am impressed.

On Fri, 19 Feb 2021, Hans Summers wrote:

Hi John
Whatever smokes, it won't be that regulator :-D 
And remember, all Rev 2 boards have been through my super-duper test jig and passed its 21 tests. All 1,000 boards. Yes the test jig really did survive that beating!
73 Hans G0UPL
http://qrp-labs.com
On Fri, Feb 19, 2021 at 3:04 PM <john@g3ztu.com> wrote:
Hi Hans,
that was quick!  Thanks for getting back, saves me a fiddly job.
Others reaching the same point may see this thread and know they can skip the mod.
I've enjoyed the build, now girding my loins for the smoke test!
All the best, and thank you!
John
G3ZTU


Mont Pierce KM6WT
 

On Fri, Feb 19, 2021 at 03:54 AM, Hans Summers wrote:
The only changes to the Rev 2 PCB are the change of voltage regulator to 78M05; and moving some components in the immediate area to make space for it (as 78M05 is larger than AMS1117). 
You forgot to mention, also a different, more reliable, PCB Fab House.  :)  :)  :)


Great Service Hans !!!   Thanks !!!
Mont - km6wt


Tom Clifton
 

Is there a photo of your test jig in action on the QRPLabs website?


john@...
 

Hi Hans,
No smoke (!), all calibration adjustments behaved exactly as documented, 4W out at 12V. 

It was a pleasure to build, and I can see some fun ahead!
I cannot tell you how impressed I am.  Thank you so much. 

73
John G3ZTU