how to discharge giant cap

[Se7en]

my astron rm-50a switch went out. need to dis charge the two 21.5V capacitors before removing the switch ... one of the wires is hot. there is three wires. anyone know the voltage to the switch?
contacted astron through email but want to get this done tonight

 

[Robb]

First of all, unplug the power supply from the wall.

If you are referring to the two disc capacitors on the switch - that keep the switch contacts from getting burn arcs on them - that shouldn't be a problem. The caps to concern yourself with are the LARGE electrolytic caps on the step down side of the transformer. But you shouldn't worry about them; you are working on the AC side of that transformer circuit - UNPLUGGED from the 110 VAC!

BTW - It is unplugged from the wall - right?
lol!

 

[wcsd106]

One side of those electrolytic caps should be connected to ground. The other is connected to positive. Get a good insulated screwdriver and short the connections on the caps. If there's any juice left in them you may here a loud pop. After that you should be pretty well safe to go.

 

[Happy_Hamer]

How to Discharge a Capacitor | eHow.com

 

[Happy_Hamer]

While it is also possible to use a small screwdriver to connect the capacitor leads, the amount of current discharged may melt the screwdriver's tip or the copper on the circuit board if the capacitor is still connected to it.

Particularly large sparks can fry power supplies or turn melted copper or solder into a projectile that can injure you.


Large capacitors are extremely dangerous and others are often in the vicinity of one you might attempt to work on.

Working with them probably isn't best for a typical hobbyist.​

 

[Happy_Hamer]

Capacitor discharge-discharging capacitors with right methods

 

[Captain Kilowatt]

my astron rm-50a switch went out. need to dis charge the two 21.5V capacitors before removing the switch ... one of the wires is hot. there is three wires. anyone know the voltage to the switch?
contacted astron through email but want to get this done tonight

Make sure the supply is unplugged. Yeah, I felt compelled to say that. The 21.5 V caps should self discharge when the supply is turned off. if they don't yiu can discharge them yourself. I don't like throwing a dead short across storage capacitors as they can carry enough energy to melt a spot on your large screwdriver or actually can be damaged by the sudden extreme current flow. For low voltage like 21 V I use a clip lead connected to ground and a resistor of about 100 ohms or so in the other end. Value is NOT critical. Touch the resistor to the cap for a few seconds to drain it.

I still think the capacitors will have self discharged anyway.

BTW, those three wires on the switch are: AC hot lead to switch, AC out from switch to load, and the third wire either goes to ground or to the other side of the AC line and is only used to light the indicator lamp in the switch.

 

[Se7en]

i would feel more confident attaching a led to it or something to discharge then a screw driver. i don't want to risk burning up anything. i always unplug power supply and wait till output shows less in mV.

the reason i ask all this is because i bought a switch same size but green in color instead of raspberry red. the switch is same size and says: Rating: 15A 125/250V AC, 1/2 HP 125V AC 1 HP 250V AC SPST 12V Lamp, Mounting hole .453" x 1.110".
light went bright in switch and blew out....?

About the capacitor I'm talking about the two that are the size of co cola cans LOL. not dinky little ones

Unfortunately the only way to remove my old switch ( to get ratings ) is by breaking the tabs out of it, either that or doing serious extracting of side panel and transistor.

@ KC no they stay charged i left meter on them and came back 30minutes later to still see 21V !

 

[Captain Kilowatt]

@ KC no they stay charged i left meter on them and came back 30minutes later to still see 21V !

Wow. Any 12 V PSU I have ever had self discharged after that amount of time do to current leakage in the regulator and output protection circuits. An LED will still need a resistor to prevent it from blowing so why not just use a 100 ohm resistor of about 2 watts rating? Discharging caps is no big deal especially the low voltage ones like these. Just remember that they pack a lot of energy and a dead short is not really the best way to do it.

 

[hookedon6]

Wow... Just remember that they pack a lot of energy and a dead short is not really the best way to do it.

heck,.............. i kinda like it when my screwdriver gets arc welded to the chassis

 

[Se7en]

heck,.............. i kinda like it when my screwdriver gets arc welded to the chassis

:laugh:

 

[RatsoW8]

I used my thumb once when I was 16 years old to discharge the cap on a 6lq6 based amp I built. Found the screw driver is the better way to go

 

[Superidgit]

Morse I agree with CK's method. Another way you could discharge them is instead of a resistor use a lamp. Might be difficult to find a lamp that will handle 21V though. Also it would be a good indicator when fully discharged.

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[Se7en]

Morse I agree with CK's method. Another way you could discharge them is instead of a resistor use a lamp. Might be difficult to find a lamp that will handle 21V though. Also it would be a good indicator when fully discharged.

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where can i get a lighted green rocker switch to replace? if you can find on eBay or even better google shopping.

 

[Superidgit]

where can i get a lighted green rocker switch to replace? if you can find on eBay or even better google shopping.

Thats a tuff one more I just searched my favorite supplier and Nada.
http://www1.mscdirect.com/eCommerce...261984&005=16934860&006=8056793104&007=Search