Recently I bought another HD20 and tried to initialize it with Macintosh SE and it froze the SE or give me error message no mather how much I tried and tried with diferent System Software versions. I tought, oh no another dead HD20 I have no luck, anyway I then conected it to the Mac Plus to see if the drive is really bad but it worked immediately ...

From now on I would not try to test or initialize HD20 on other Mac than Plus