[Ovmsdev] USB port fragility

Mark Webb-Johnson mark at webb-johnson.net
Tue Aug 4 14:50:07 HKT 2020

In this batch we tried to address the reported / experienced problems:

USB port dislodged with rough handling - change was to increase solder pad area and adjust thermal profile when soldering
Large capacitors dislodged during shipment - change was to increase solder pad area and adjust thermal profile when soldering
Reports of GPS Antenna non functional (no continuity) - change to new (more robust) internal antenna cable

We have also seen #3 seen internally, during random QC checks, with the GSM Antenna (although no reports from users).

If you remember, back when v3.2 was released we had to change that internal antenna cable (due to ROHS issues with the type of plastic used). Since then we have had a number of reported issues with GPS reception that were traced back to poor contacts or no continuity with these internal antennas (particularly the batch late last year). So, we (a) add a QC step to check continuity and ‘wiggle’ the antennas to ensure they are stable, and (b) change the component to a ROHS compatible antenna similar to the previous one we used. The new component feels much more solid (particularly when connecting to the modem PCB) and so far tests 100% with no QC failures.

Regards, Mark.

> On 4 Aug 2020, at 2:39 PM, Michael Balzer <dexter at expeedo.de> wrote:
> Great, that looks much more rigid and should solve the issue.
> What's the reason for / benefit of the thicker antenna cables? Also just rigidity, or do they have an effect on signal strength?
> Regards,
> Michael
> Am 04.08.20 um 03:24 schrieb Mark Webb-Johnson:
>> The small solder area is my suspicion too, and a relatively easy fix. Through hole would be better but would require a new component and circuit redesign (with associated complexity and re-certification issues). Here are some pictures of the 2020-06-15 batch with the changes. But it will be some time before distribution stock is cleared out and those start to be shipped. Note also that 2020-06-15 also includes a change to new thicker antenna cables for both GPS and GSM.
>> Regards, Mark.
>>> On 4 Aug 2020, at 9:11 AM, Craig Leres <leres at xse.com <mailto:leres at xse.com>> wrote:
>>> On 2020-08-03 01:26, Michael Balzer wrote:
>>>> I've had multiple cases now of damaged and broken off USB ports.
>>> I managed a mechanical "no heat" desolder of the usb port on one of my modules last year (I wasn't careful when sliding the seat back with a cable plugged in). When I took it apart I could see that there was not very much solder in the four holes that secure the usb shell to the board. At the time my suspicion was that the small amount of solder from the factory wave solder made for a weak bond. I was lucky that I didn't lift any pads and was able to resolder it.
>>> 		Craig
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