For those who are too impatient to read to the end the answer to B) is Yes and No. Yes, it is *easily* repairable. No, because the cells have been designed so as make them non-serviceable. Quite frankly this makes me a bit perturbed as it makes ABSOLUTELY no sense to spend $500 when a $50 repair will suffice. Now, on to dissection.
The salt cell as it was removed. It was provided by the pool builder, and has been in service since summer 2003. The seam underneath the label is melted or welded together, and survived quite a few sharp blows that I was hoping would cause the seam to fail.
The cell cut open. Only plates 1, 7, and 13 are connected. 2-6 and 8-12 are simply held in place by the plastic guides. These plates correspond directly to the connections seen above.
Visible on the bench are the 10 loose plates. As you can see, they show VERY LITTLE evidence of erosion and no evidence of scale or calcium buildup.
Note: This cell failed suddenly after 9 years of perfect service. Obviously at some point the contact post (which appears to be brass) separated because of galvanic corrosion. Not really a surprise as the anode only has one connection, while the cathodes have two.
A close up of the failed center stud. Plate erosion is minimal.
All three plates together
Comparing a good edge post with the failed center post.
And finally a close up of the "active" plates next to the "passive" plates. As you can see, actual damage to the plates is minimal.
After 9 years, there is almost observable no damage to the plates, and the cell was performing perfectly until it up and quit. In fact, the only place where noticeable erosion exists is where dissimilar metals are joined, so I suspect the failure is not use but galvanic corrosion. If so, the design should be correctable with a sacrificial anode.
I suspect a large number of these cells are failing because the "anode"(1) stud separates, as mine did. If the case were not sealed, I would have acquired several "dead" units and salvaged plates to make mine workable again.
In a nutshell, I am of the opinion that we are getting fleeced on these cells because a sealed design makes for a larger profit margin.