Grounding chassis through RCA

[tomchr]

Originally Posted by quikie22

Why would this work better than a simple resistor and capacitor? I understand the role of the capacitor, which I would also include.
But the diodes? What does he mean by a "major problem"?

I think the resistor value shown is actually a little too low. I would still stick to something in the region of 30-100 ohms.

The diodes are there to limit the voltage across the resistor in the event of a short circuit to the chassis. Without the diodes, the resistor would blow and you'd end up with a 'hot' chassis. With the diodes in place, the diodes conduct when the ground current causes the voltage drop across the resistor to increase beyond two diode drops (1.5~2 V). This will cause significant current to flow and blow the mains fuse or circuit breaker.

~Tom

[Bengali]

The diodes are there to limit the voltage across the resistor in the event of a short circuit to the chassis. Without the diodes, the resistor would blow and you'd end up with a 'hot' chassis. With the diodes in place, the diodes conduct when the ground current causes the voltage drop across the resistor to increase beyond two diode drops (1.5~2 V). This will cause significant current to flow and blow the mains fuse or circuit breaker.

what should the rating be for the resistor? I've been using 10R 1W per different soundwesthost article. the one in this post says 5W wirewound.

I have not used the diodes and probably will add them from now on.

[Sheldon]

Originally Posted by Bengali

what should the rating be for the resistor? I've been using 10R 1W per different soundwesthost article. the one in this post says 5W wirewound.

I have not used the diodes and probably will add them from now on.

The diodes are much safer than a resistor alone. Even if the diode is not quite adequate, and it fails, it will fail short. The resistor will fail open. So use nice fat diodes (you can use a cheap 20W bridge). Then, if you want to use a resistor too, it can be a regular 1.4W part.

Sheldon