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06-03-2016, 07:53 AM   #1
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Do flash capacitors discharge over time?

Having had the camera without battery for more than a week, can I expect the flash capacitor to be discharged by that time? I am going to open the case of my K-30 to repair the electromagnet that controls aperture and want to make sure that when opening I do not damage any circuit or myself.

06-03-2016, 08:06 AM   #2
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Yes, all capacitors do. How long it takes depends on a few factors though, so it is always wise to take precautions.
06-03-2016, 08:13 AM   #3
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Since the insulation is not 100% effective all capacitors will "leak" charge (discharge) over time. How long depends how efficient the insulation is. One week is probably not enough time to discharge the capacitor unless it is very old. It is common safety protocol to never assume the capacitor is discharged.

The K10D service manual says to use a 100-1000 ohm resistor to discharge the capacitor. I would use around a 2 watt ceramic resistor. The resistor will get hot while it discharges the capacitor. These should cost you a 2-3 bucks at Radio Shack or under a buck at any decent electronics supply store.
06-03-2016, 08:16 AM   #4
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QuoteOriginally posted by JoseFF Quote
can I expect the flash capacitor to be discharged by that time?
I don't know what size of capacitor is used for the built-in flash on a K-30, but it can't be very big, it takes very little power to charge it. There are probably diodes in the circuit to prevent a discharge from going anywhere but to the flash tube. I'm not the electrical engineer who designed this flash, but after a week it should be safe from an accidental discharge. Is it necessary to open the circuit to the flash tube to get at the electromagnet that moves the aperture lever?


Last edited by RGlasel; 06-03-2016 at 08:23 AM.
06-03-2016, 08:24 AM   #5
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Tread very carefully around flash capacitors. I get zapped frequently, despite my best efforts.

They do stay charged for quite a long time. If you know the camera hasn't been powered up in the last year, I would say it's safe. Less than that, tread carefully.

Keep in mind that even if you can see the capacitor, you can't always be sure of what it's hooked up to. Touch one innocent looking wire on the edge of a board, while touching the grounded chassis with your other hand, and you might end up tossing the camera across the table and off the other side - depending on how your muscles spasm.

I have a special gadget made by ZTS especially for discharging camera capacitors. It buzzes until the cap is depleted. It was stupidly expensive, considering what it is. But it has saved my fingers many zaps over the years.

Doesn't get 'em all though.
06-03-2016, 09:17 AM   #6
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This is a high voltage circuit, no current to speak of. But they will still light you up, and It won't care if they knock you across the room. In old tube type TVs, some capacitors can hold a charge for 10 years or more. so you'll be well advised to not trust any capacitor, especially a high-voltage Capacitor. always discharge them properly. Even if it has just 100V on it, it can still be shorted to another component and damage that component. Be careful, and stay safe.

Note: even if you set off the flash without a battery in it, the capacitor can still maintain some voltage. I have had a flash that would, on a low setting, Flash several times without a battery in it. Do not trust That they have been discharged. Always Discharged them Manually.
06-03-2016, 09:24 AM   #7
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QuoteOriginally posted by RGlasel Quote
I don't know what size of capacitor is used for the built-in flash on a K-30, but it can't be very big
That's what I assumed of a Canon A85 but the capacitor ended up being about 10% of the volume of the camera. Gave me a nasty shock I can tell you that
06-03-2016, 09:58 AM   #8
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QuoteOriginally posted by RGlasel Quote
it can't be very big
QuoteOriginally posted by Giklab Quote
Canon A85 but the capacitor ended up being about 10% of the volume of the camera.
I've been inside a Canon P&S, and the capacitor in the K-30/50 is bigger than that. It's rated at 240 F & 330 volts, is about the size of an AA battery, and takes up most of the "short grip" on the side away from the battery.

06-03-2016, 11:30 AM   #9
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QuoteOriginally posted by promacjoe Quote
This is a high voltage circuit, no current to speak of. But they will still light you up, and It won't care if they knock you across the room. In old tube type TVs, some capacitors can hold a charge for 10 years or more. so you'll be well advised to not trust any capacitor, especially a high-voltage Capacitor. always discharge them properly. Even if it has just 100V on it, it can still be shorted to another component and damage that component. Be careful, and stay safe.

Note: even if you set off the flash without a battery in it, the capacitor can still maintain some voltage. I have had a flash that would, on a low setting, Flash several times without a battery in it. Do not trust That they have been discharged. Always Discharged them Manually.
TV picture tubes themselves can constitute a capacitor! The two HeathKit color TVs I built had strong caution warnings about this since the tube had to be handled for installing in the set. The HV anode connection had to be shunted to ground through a resistor of perhaps 10K ohms, using a screwdriver with a plastic handle. This procedure was the "scariest" part of the whole operation, other than the risk of snapping the tube neck, which might result in the implosion of the CRT.
06-03-2016, 11:37 AM   #10
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QuoteOriginally posted by THoog Quote
It's rated at 240 F & 330 volts, is about the size of an AA battery
Wow, that's almost like a hi-fi amplifier! Good thing I'm not servicing cameras, that's all I can say.
06-03-2016, 01:22 PM   #11
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Power in is not the same as power out. DISCHARGE it and be safe, please.
06-03-2016, 02:58 PM   #12
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Some of you might dispute this as impossible- but it is TRUE! An electrolytic capacitor can re-charge itself to some degree even after being shorted to discharge it. I've seen it myself, though I didn't believe my eyes at first. Watched the voltmeter reading creep back up. Later read an article explaining the phenomenon. Charge gets stored in the electrolyte and can migrate back onto the plates after a 'complete' discharge. So, to be safe, keep the leads shorted while you are working around the cap.
06-03-2016, 05:28 PM   #13
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It is always safest to discharge the capacitor, not just for yourself, but for the surrounding circuitry. You will forget to do it once, maybe twice and then after the initial shock or two wears off, you will have it set in your head! Wearing a static discharge arm band is also good. It will reduce some of the initial pain!
06-05-2016, 04:42 AM   #14
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QuoteOriginally posted by JoseFF Quote
Having had the camera without battery for more than a week, can I expect the flash capacitor to be discharged by that time? I am going to open the case of my K-30 to repair the electromagnet that controls aperture and want to make sure that when opening I do not damage any circuit or myself.
No but I forgot to discharge it once , it wont kill you it is like one of those shock toys
06-05-2016, 10:03 AM   #15
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QuoteOriginally posted by niceshot Quote
it wont kill you
but pregnant women and people with pace makers should be extra careful!

Regards,

BD
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