Simple notion.

Tweakers' Asylum

Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

Simple notion.

Posted by Al Sekela (A) on November 1, 2010 at 11:03:11

In Reply to: RE: That is a good idea. posted by Capt. Z on October 31, 2010 at 18:11:45:

Connect two silicon junction rectifier diodes in anti-parallel and wire the result in series with the safety-earth connection. The diodes should be big and beefy to permit fault current to flow long enough to trip the circuit breaker. Because the diodes are pointing in opposite directions, there is always one that permits current to flow with no more than a single diode drop across it, no matter which polarity the AC voltage has at the instant of the fault.

This is a safety issue, as some would argue that the theoretical maximum fault current is so large that any reasonable size rectifier diodes would explode and interrupt the connection to safety-earth before the breaker trips. However, in most cases, the AC branch circuit impedance is high enough to prevent this. It is important to NOT use fancy rectifiers in this application, as they usually have less tolerance for overloads.

An alternative is to use a potted rectifier bridge with the + and - terminals wired together, and the AC input terminals wired together. This puts two diodes in series in each direction. The bigger ones come with metal jackets and are easy to mount on a heat sink. I use 35-ampere versions.

It is also possible to wire this into a power cord to try the concept before making permanent changes in your equipment.

The reason this works is that the diodes have very high impedance for small noise voltages. Since junction rectifiers have capacitance, adding some heavy inductors with about 1 microhenry of inductance in series will make the RF impedance even higher. The end result is close to an open circuit for noise voltages, but a low impedance path for fault current.

This post is made possible by the generous support of people like you and our sponsors:

Follow Ups Full Thread

Topic - Don't want to listen to AM radio - Capt. Z 15:09:34 10/27/10 (14)

First, disconnect the tuner. - Al Sekela 15:27:26 10/27/10 (13)

RE: First, disconnect the tuner. - Capt. Z 06:25:03 10/28/10 (12)

Try shorting plugs on the preamp inputs. - Al Sekela 14:56:55 10/28/10 (9)

RE: Try shorting plugs on the preamp inputs. - Capt. Z 13:39:10 10/29/10 (8)

RE: Try shorting plugs on the preamp inputs. - Capt. Z 14:02:45 10/29/10 (7)

Big ground loops make nice AM antennas. - Al Sekela 15:26:24 10/30/10 (6)

RE: Big ground loops make nice AM antennas. - Capt. Z 04:59:06 10/31/10 (5)

Based on results so far... - Al Sekela 13:03:20 10/31/10 (4)

RE: Based on results so far... - Capt. Z 14:00:49 10/31/10 (3)

That is a good idea. - Al Sekela 15:03:57 10/31/10 (2)

RE: That is a good idea. - Capt. Z 18:11:45 10/31/10 (1)

Simple notion. - Al Sekela 11:03:11 11/01/10 (0)

RE: First, disconnect the tuner. - floydandrews 09:54:07 10/28/10 (1)

RE: First, disconnect the tuner. - Capt. Z 10:56:24 10/28/10 (0)

Follow Ups

Simple notion. - Al Sekela 11:03:11 11/01/10 (0)

Post a Message!