discharge capacitor with a light bulb

Thread Starter

kahnwasim

Joined Oct 7, 2019
7
Hi All.

Im a camera lens repairer & have been repairing lenses for sometime now. I'm tempted to repair a canon which has a inbuilt flash in it, now Ive seen a capacitor in the camera with a red & black wire soldered to it. I have no knowledge, how do I use a light bulb to discharger the capacitor. first of all what do I need to build the light bulb, how to assemble it & 2nd how do I apply the bulb device to the capacitor to discharge it?.
 

crutschow

Joined Mar 14, 2008
23,291
Connect two wires to the bulb (using a bulb socket if needed).
Then connect the wires directly across the capacitor.

Just about any incandescent (not LED) bulb should work.
A small value resistor (10-100 ohms) will also work.
 

Alec_t

Joined Sep 17, 2013
10,350
Be VERY careful. The flash capacitor charges to hundreds of Volts and holds enough charge to kill you.
 

Thread Starter

kahnwasim

Joined Oct 7, 2019
7
Connect two wires to the bulb (using a bulb socket if needed).
Then connect the wires directly across the capacitor.

Just about any incandescent (not LED) bulb should work.
A small value resistor (10-100 ohms) will also work.
Thanks for your time. I’m a complete novice at this, is there any videos or diagrams to show this process how to build the bulb tester & where to Connect to the capacitor?
 

crutschow

Joined Mar 14, 2008
23,291
is there any videos or diagrams to show this process how to build the bulb tester & where to Connect to the capacitor?
Not likely, since it's so basic.
What don't you understand about my explanation?
It's a simple matter of connecting two insulated wires to the two bulb contacts, and then touching those two wires to the two capacitor contacts.
 

Thread Starter

kahnwasim

Joined Oct 7, 2019
7
Not likely, since it's so basic.
What don't you understand about my explanation?
It's a simple matter of connecting two insulated wires to the two bulb contacts, and then touching those two wires to the two capacitor contacts.
Sorry for sounding so dumb I don't know which part of the build to attach the wires. anyway I found this online & I think its the right tool for me

(commercial line deleted by moderator --yes, you can try it but crutschow's solution is just as good if not better -dc)

is this the one for me?
 
Last edited by a moderator:

SamR

Joined Mar 19, 2019
1,133
I have to ask... I keep seeing this "lightbulb" method but why? Is it a "soft" discharge or just a way to make contact with 2 not easily reached terminals by the screwdriver method? I always just grab a screwdriver.
 

SamR

Joined Mar 19, 2019
1,133
Yeah, they are all pitted up a bit. I did see one post saying to put alligator clips on the leads from the bulbs but I would be hesitant using my bare hand to connect an uninsulated clip to a high voltage condenser terminal. Does the bulb give a "softer" discharge than just crowbarring it with the screwdriver? I have had a few tingles here and there over the years but so far I have avoided getting bit hard and want to keep it that way.
 

Thread Starter

kahnwasim

Joined Oct 7, 2019
7
I’ve just ordered this, has I couldn’t find one with a bulb attached with pin points

(Second attempt to promote commercial product removed by moderator.)
 
Last edited by a moderator:

MrChips

Joined Oct 2, 2009
19,269
Flash capacitors are charged to about 300VDC,

Use a 10 to 100Ω resistor to discharge the capacitor.
 

Thread Starter

kahnwasim

Joined Oct 7, 2019
7
Flash capacitors are charged to about 300VDC,

Use a 10 to 100Ω resistor to discharge the capacitor.
Thanks for the advice. I feel more confident using a tool with a bulb to make its completely drained out. The capacitor that I’m going to discharge has a red & black wire attached to it, so I’m I right to say I touch the red with red & black with black?. Red positive & black negative, also should I touch red-red first or black-black first?
 

MrChips

Joined Oct 2, 2009
19,269
Matching the colours is not important.
You are over thinking this problem.
Just discharge the capacitor with a piece of wire (if you don't mind the loud bang!).
 

Thread Starter

kahnwasim

Joined Oct 7, 2019
7
Matching the colours is not important.
You are over thinking this problem.
Just discharge the capacitor with a piece of wire (if you don't mind the loud bang!).
I’ll be honest, I was electrocuted a year back when I opened a camera, I thought it was safe to touch the insides because the battery was removed. I had loud bands
 

Tonyr1084

Joined Sep 24, 2015
3,555
Just touch both leads of the capacitor at the same time with a pencil lead. The lead will conduct the energy and discharge the capacitor. Screwdrivers or other metal objects will get pitted. With a pencil lead - no problem. It offers some resistance, drains the cap fast, and is easily sacrificial. Just make sure the lead touches both leads at the same time.
 

DickCappels

Joined Aug 21, 2008
5,873
Please DO NOT touch a conductor (the insulator should be ok if it is rated for the voltage) that is being used to discharge a capacitor.
 
Top