I have three of these flashes that I've converted to manual flashes. One
works ok, The second i have to turn on and off several times, but it
finally starts whining, and works perfectly thereafter so long as it stays
on.

The third used to do that too, but now it won't whine at all. I've taken
it apart, and the main capacitor checks out good, as does the main power
switch. So I'm left with tryng to figure out why the boost circuit doesn't
start up - doesn't oscillate. The smaller electolytics look ok, but I
haven't taken them out to check them. And of course there's no schematic.

I'd like to find a fix, but I don't want to make a second career out of it
either. Any suggestions on what to check, or how to approach this?

Thanks very much.