Dave Plowman (News) wrote:
In article . com,
Just Another Theremin Fan wrote:

It is a FACT that capacitors DO sometimes go short circuit and although
it is some time since I worked on domestic equipment I simply cannot see
a such potentially dangerous practise as caps' directly connected to
external metalwork from the mains getting past the design stage.


IIRC, they're not normally connected direct to the signal earth or case
but via a high value resistor. And those don't fail short circuit.

RFI suppression using this sort of technique has been common for probably
30 years or more. The usual answer is to plug in the signal leads before
applying the power - which is good practice anyway.

Any resistor would make them totally useless.
The cap resitance must be near zero for high
frequency's.And plugging with power off does not
protect your inputs,the filter comes before your
main switch, and the cap current can damage
a mosfet input,even if it is only microamps,the
voltage is half the mains voltage,when there is
no ground path.