I used SanDisk and Lexar, and a couple of other name brand SD cards. Made no difference. The usual barrage of replies on the RPi forum, was:
"You're overclocking your RPi"
No I wasn't.
"You're using the wrong SD card"
I was using a good SanDisk SD card bought from a reputable computer store.
"You're using the wrong model SanDisk SD card"
I was using one of the models specified on the official RPi approved parts list.
"You should only use the SD cards that were manufactured on a Tuesday afternoon in months ending in R"
And so it went. And I'm not joking. It really reached this degree of farce. If it won't work with any make/model of SD card, then let's put the blame where it really belongs. The RPi had a serious design flaw, and the designers were in a permanent state of denial.
If they had actually admitted there was a problem, then I might have had the confidence that they would attempt to fix it in a later version. But, if they would never acknowledge the problem, I have no reason to believe that it was ever fixed.
Sorry if I'm sounding crabby. This is all bringing back bad memories. I think if I do anything with the old RPi board, I'll try one of the mods that makes the SD card read only.
Measuring the power at the chip pins is easier said than done. The SoC has a second piggyback chip on top. None of the pins are accessible.