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[email protected] tabbypurr@gmail.com is offline
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Default Vivitar 3500 "zoom thyristor" flash won't whine

On Monday, 14 September 2020 01:22:16 UTC+1, Ralph Mowery wrote:
In article ,
says...

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?



If there are any small electrolytic capacitors I would chanage them.
Many switching supplies have the problem where the capacitors go bad.
One way that may help confirm that is to take the one that sometimes
works and heat the capacitors with a hot air gun or even a hair dryer
and then try starting it. If it starts up faster the capacitors are a
sure bet.


Another other way to test them is to piggyback a new one on, see if it springs to life. Another way is to use a component tester.


NT