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  1. #11
    Mike Wilde's Avatar
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    Low tech solution if it is a battery powered flash - turn it on with fresh batteries, and leave it on at first without discharging the flash immediately.

    I would suggest 20 minutes on standby, pop the flash once on manula, reduced power if there is a way at first, then shut it off and repeat this for a few days.

    This is a low tech way to reform electrolytic capacitors.

    I have a poweredful older line powerd studio flash, a Speedotron 2401.
    With it you can actually hear little arcs and snaps from time to time for the first 20 minutes of conditioning, if the flash has not been used for a while.

    I am not super diligent, but I do try to condition the studio flash pack every three months if it has been otherwise idle.
    The power packed into the big caps in thia unit can leave a a lot of havoc behind when they blow. I have seen some fried examples at the repair depot over time.
    my real name, imagine that.

  2. #12
    Mike Wilde's Avatar
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    To further Matt's comments , bigger flash do well by slowly building the supplied DC voltage to them if they have been idle for a while.
    my real name, imagine that.

  3. #13

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    That's good to know too, I have some studio strobes that haven't been used in a while, I'll be sure to do that.

    This has been a very helpful thread! I understand that this won't really wake up a dead cap, but its good to know it won't hurt an old one.


    -Xander

  4. #14
    mr rusty's Avatar
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    Please treat flash caps with caution. Once I shorted a flash cap with a screwdriver expecing just a little spark. The bang was something else. Sure won't be doing that again in a hurry.

  5. #15
    Mike Wilde's Avatar
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    I have a straight bladed screwdriver with one corner that has been vapourized away. It dissapeared with a sound akin to a shotgun being discharged right next to my ear.
    I keep it in the tool bag as a reminder to not be so stupid again

    The next time I serviced a flash I was sure to bleed off the cap by shorting it though a 1 megohm resistor for a few seconds.
    The one that blew the screwdriver and my hearing temporarily had been powered off overnight.
    my real name, imagine that.

  6. #16

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    [QUOTE=Mike Wilde;1554109 by shorting it though a 1 megohm resistor for a few seconds.
    .[/QUOTE]
    That will hardly begin to discharge a typical flash capacitor of 250 uF charged to 300 Volt
    (See my earlier post)
    The way it works is, Time constant [seconds] = Resistor {ohm] * Capacitance [Farad]
    The capacitor will still have 33% charge (say 100V) after being discharged for one time constant so you have to leave the resistor on for about 6 times longer

    Take care!

  7. #17
    Steve Smith's Avatar
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    Quote Originally Posted by wombat2go View Post
    For an average flash capacitor, let me say a 10,000Ohm 20 Watt resistor
    On valve (tube) equipment with similar voltages, I usually put a 100K bleed resistor on one of the capacitors. It only needs to be about 1 watt rating.


    Steve.

  8. #18

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    Quote Originally Posted by Steve Smith View Post
    On valve (tube) equipment with similar voltages, I usually put a 100K bleed resistor on one of the capacitors. It only needs to be about 1 watt rating.


    Steve.
    Typical Flash 250 uF 330 V Nom initial discharge power = V^2/R = 330 *330/100000 = 1.1 Watt
    1 Watt might be OK for tube Hi Fi etc where the voltage is lower.

    i prefer the wirewound with safety factor and posts so the insulated leads last longer before breaking off
    a 20 W resistor is OK right up to 1 kiloVolt ( I work with industrial capacitors too)
    The high potential capacitor testers usually have an inbuilt discharge which is safer than messing around with clip leads etc.
    Attached Thumbnails Attached Thumbnails FlashDisch.jpg  

  9. #19

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    Well to give an update. I received the flash and loaded an old set of cells in it. They wouldn't even get the cap to make noise at first, so a good thump or two got it going. The cells were further drained than I had thought, wouldn't even bring the flash to ready, so I just left it for 30 minutes to sit. It finally got enough juice for one last flash. Switched the batteries out for a fresh set from another flash and it ramped up pretty good but again not right away. After doing the flash and sit routine for half a day it seems to be just fine now with fresh cells!

    Its not a very advanced flash, manual push/pull zoom, decent power range and 180 degree pan/tilt head. The bounce reflector is something I haven't dealt with before, its clear with a matrix of silver ovals on it. The color cast is quite nice though. It'll just be another working piece of kit now.

    Thanx all for the help!


    -Xander

  10. #20

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    Reforming Speedlite Capacitors

    ​Some time in the distant past, when I was still buying new gear, I read the owner's manual for a Vivitar unit [could have been a 283 or 285] that had a section devoted to reforming the unit's main capacitor after a long idle period. As I remember, the procedure was to load fresh batteries, switch the unit to manual and full power, power on, let the unit light its Ready lamp for thirty seconds before pushing the Test button, and repeat for a total of five cycles. The first charge cycle could take long enough for you to get real antsy, holding the unit close to your ear to be sure the voltage multiplier oscillator circuit was working, but by the fifth time around, the unit would be recycling in a much more reasonable time.

    I just took delivery today of an 'AS-IS' Sunpak 611 that was marked 'won't power up' and ran through the procedure after running an emery board across the battery cover contacts. The unit needed a few more than five flash cycles before lighting up its 'FULL' indicator lamp, but it looks like it will be OK for use.

    Best regards,
    Vince

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