Done all that – I've run dozens of floppies through it, and no jitters whatsoever at any stage. I haven't done a serious check for dodgy solder joints yet but it's on my maintenance list. At least it looks like there are no immediate obvious problems.

I'm mainly relieved that the 'delay' in startup is a normal function – I thought it was maybe a symptom of analogue board problems. It's good to know it's just the normal memory check. And my machine came with 4MB of RAM