Turns out that the drive is OK. What was wrong was a bad memory stick. After getting the hard drive reformatted I still couldn't install the OS on it. Ran the Hardware test and found that one of the 2 GB RAM modules was bad. Pulled it out and now all is well. (Except that the MacBook now has 2 GB RAM instead of 4....)

"Simulated sine wave at 220Vac ±5%" = modulating a switcher to look like a sine wave. A UPS output (unless well filtered) can have some nasty high-frequency crap on it and it tends to get worse as you approach the full power rating. A good downstream power supply can ignore that although it tends to heat its transformer, but power bricks are not so good -- typically rather cheap -- and pass some of that on. Could it be that the drive power supplies and bridges are just suffering from that? That's probably why AMO suggested a scope.

Assuming that you are at Suranaree, given that you live in Korat, I'm wondering if you can't ask a friendly engineering prof, technician or student to have a look at the output of the UPS under load. When I was there many years ago, they had an Engineering School.

That's very possible and perhaps explains why it's only drives and why none of the other gear (computers, routers, TVs, etc) have had any failures at all. I only have one drive left that's not bus powered.

Were you working at Suranaree? I'm retired and don't have any contacts there.

I didn't work for them, I was part of a Canadian International Development Agency team as Dean of Engineering at a school here in Nova Scotia to help Suranaree mount a graduate program in Engineering. Brutal trip from here though -- last time I went it took 29 hours counting wait times but not an overnight. First Toronto, wait, Vancouver, wait, Hong Kong, wait, Thai Air to Bangkok, overnight, early flight over the mountains to Korat. On the way back, we did the tourist routine in Bangkok.

Loved Thailand (and I'm very fond of Thai food). People were wonderful.

You must have done well. Suranaree is now ranked very highly among universities in Thailand. Pretty decent given that it's only been around for a couple of decades.

I'm glad to hear that -- I haven't followed that since I retired 9 years ago. The folks there were extremely gung-ho and very easy to work with -- the credit is theirs.

Why do you have several UPSs if the power is rock solid?

Because the power does go out now and then; hence the use of the word "generally". Lightening hits a transformer. Drunk hits a power pole.

If I'm home I like to gracefully shut down the machines if the power goes out.

If I'm not home. Well. Too bad.

Perhaps I've been very lucky, but I've had the power go out over a broad range of machines I've owned and as far as I could tell afterward, I've never lost a byte. Is that just luck? There's no risk to my backups because they're only powered up while a backup is in progress.

What's luck?

About a year ago I started getting flat tires on my bicycle about once a week. None of them were punctures; just what seemed to be manufacturing flaws: tiny pinholes in the tube, lamination failures at the valve, etc. I tried tubes of various brands from several manufacturers. The flats continued for weeks. And then they suddenly stopped and I haven't had an unexplained flat in six or eight months. Luck?

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Maybe my use of UPSs dates from my time (25 years) on Saipan where the power was really awful. Constant outages, brown outs, spikes, etc. I had protective devices on anything with a motor and a compressor and voltage stabilizers and UPSs on the computers, TVs, etc.

In my office we had a massive UPS that took up an entire room and used 30 or 40 car batteries.