If you have a bench grinder, you can get a wire brush attachment for it. You can use that to clean the PVs faster and more efficiently than by hand.

Have you checked that your PVs are getting stuck? It would be such a waste of time to take them out and then to find they are clean as a whistle

If you're free tomorrow, you can pop round to my place and we can test the 2x regulator/rectifiers that I have.
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Jerry Lai
NSR250 [MC21SP]