The most destructive thing for large high voltage electrolytic
capacitors, is the discharge cycle. It rapidly collapses the
capacitor and this is what eventually causes shorts within the
capacitor. A charged capacitor keeps everything formed and in order.
I have absolutely no idea why Speedotron would fire the unit upon
power off unless it's so one does not short out the unit by removing
connectors (heads) when the capacitors are still hot. I have a half
dozen Dynalite packs. They do not do this. I've never worked on a
Speedotron. I've never worked on a unit that fires the lights when
powering down. Some units slowly bleed off the charge through a large
resistor so that should the unit need to be opened-up, the technician
won't get electrocuted. It hurts! I know!
Ask any EE worth his salt about forming and collapsing electrolytic
capacitors and they will tell you what I did earlier. Don't rapidly
discharge a large high voltage capacitor and then not reform it. That
is, don't fire a strobe unit after the power is off, leaving the
capacitors collapsed.
BTW, Oregon State (Corvallis) 1955-1959, EE. Brooks Institute of
Photography 1959-1961, commercial photography.
As far as someone having a unit that works after years of leaving the
capacitors collapsed, well, there are people who smoked a pack a day
and lived to be 100. I'm simply explaining the physics of the care
and feeding of large high voltage capacitors. There are always
anomalies, and like anything else, there are quality variations in
the manufacturing of everything. The best way to insure long
capacitor life is to treat them properly. Re-form them immediately
upon discharge. Leave them formed (full) or discharge them slowly
through a large resistor at power off.
Jim
At 11:47 AM 10/2/2006 +0200, Ralph W. Lambrecht wrote:
The Speedotron units do this as a matter of operation. When you turn the unit off, it fires all lights. Speedotron suggests to turn the power to full before turning it off to discharge the capacitors. Why do you think they suggest that? Or did I misunderstand something?
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