Hi !
I can second this (and Richard capacitor's blow..)
"been there, done that".
I've got a strobe capacitor blow because it has dried dur to long
storage in bad condition (and maybe misconception of the strobe).
When powered up a huge whitsle and BANG the capacitors exploded, making
a total mess of the strobe. Hopefully, the package did not explode, and
contained all the "stuff" inside so no one got injured....
Now, I only use portable strobe, and when planning long storage fully
charge them before turning them off and removing batteries. So far, no
problem (except that one old Metz torch sucked up one complete batterie
set to return to servicce....)
Treat these mighty capacitors with their due respect.... As you'll do
with television very high voltage... if you plan to live old !
Jim Brick a écrit :
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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