Joe
The rotary switch contact holder has a 3 split shaft with little tangs that grab the back of the PCB. The height of these tabs minus the PCB thickness was probably what determined the compression of the contacts in the original design.
I agree and stated that in the video.
I think the idea of the shim was to provide more compression without having to remold the plastic contact holder.
Per Dave, they want to use a thicker PCB. Personally, I don't think they have a clear understanding of the root problem. The original prototype had some major wear problems so when they added a shim after the release, I wasn't all that surprised to hear they were still fighting a mechanical problem.
You didn't measure the height of the tabs, but since the shim is still present one can conclude that the new meters ae same as old except with shim pre-installed.
I measure the PCB thickness and the height of the contact holder to the bottom of the PCB. I also measured the resting height of the contacts dimple to the bottom of the contact holder. None of these have changed. From a mechanical standpoint in regards to the switch, the contacts are now plated, the contacts now use a single dimple rather than two and there is an addition of a shim.
The shim is not necessarily a bad idea, although a tolerance analysis of the resulting stack-up would surely prove otherwise, but maybe proper height tabs caused too much friction and subsequent debris or since the contact load is in a straight line perhaps the assembly would cock off axis which the shim would prevent.
On most meters I have looked at where they use a hole in the PCB as part of a bearing surface, they have it plated. In the case of the prototype without the shim, the debris was not from this area but from the contacts and pads. Until I run it, it's just a guess on how it will hold up to the 50,000 cycle test. I understand what you are saying about it going off axis. The center of the plastic contact holder is locked in place by the hex shaft. Of course that could go off axis as well.
As far as the shim idea, having looked at the prototype and seeing the wear first hand, I have been concerned about the switch design ever since. After hearing they added this shim as a last minute fix did nothing to improve my confidence. I openly stated that the reason I did not buy a production meter was in hope that they would address the problems that caused them to add the shim. Per Dave, a thicker PCB. I think the last time I saw an update on this was during one of the Amp Hour shows. That's been several months ago. I felt allowing them two years to sort out these problems was more than fair enough. So, what happens when I try some simple tests to check out the meter? As you saw, it appears as though the shimmed switch is still having problems.
I wouldn't be at all surprised to hear about a new revision once I finish this series.