Draining caps

[pnutbutters]

Can you drain caps in-circuit (for testing purposes)

How do you drain them safetly?

Do you have the drain the ceramic capacitors (small square cap's)

[Topcat]

Re: Draining caps

Just short them with a test lead or a screwdriver.

[tom66]

Re: Draining caps

Never really found a need to do that unless they are high voltage. They do not present a risk of electric shock. Many ESR meters and multimeters with cap functions will automatically perform a controlled discharge of the component before testing.

[Uranium-235]

Re: Draining caps

unless they're high capacitence caps, do what tc said

if they're like 10000uf or higher, expect a nice pop if you short them. In middle school, my dad had an oil cap he got from his father (worked his own A/C repair business). 'Twas fully charged, and he shorted it against his desk, blew a hole in it

[rilski]

Re: Draining caps

So I guess it's safe to say that values that are found in most Motherboards ranging from 1500 ~ 3300uF are safe to use the "screwdriver method"? hehe

[retiredcaps]

Re: Draining caps

So I guess it's safe to say that values that are found in most Motherboards ranging from 1500 ~ 3300uF are safe to use the "screwdriver method"? hehe

The highest voltage you will find typically on a PC motherboard is 12V DC as that is what the ATX power supply ouputs maximum (along with 5V, 3.3V).

Inside an ATX power supply, you may encounter up to 400V DC on the large filter cap depending of the presence of PFC.

[kc8adu]

Re: Draining caps

no need to esr test most mobo caps on board much less discharge them.
too many in paralell and often bypassed with mlcc.
with vrm's that run on whats in the input caps to all the pullup/pulldown resistors nothing stays charged.