TV Guard

Here is a simple solution to protect TV from voltage surge through cable during lightning. It gives protection, if the induced current is not too high. The circuit uses only two Safety capacitors to limit the voltage entering into the antenna input of the TV. This can be also used in Modem cables.

The circuit does not require a PCB or soldering. The safety capacitors can be serially connected to the core and shield of coaxial cable as shown in the circuit diagram.

Safety Capacitor

Safety Capacitors are designed to withstand high impulse voltages in applications where human beings might be exposed to voltage surges. These capacitors will shunt the energy from the impulse to ground, protecting the circuit from the surge. Safety capacitors are available in ceramic disc and metalized film or paper. The film type are made of self-healing metalized polyester, polypropylene or paper and usually come in a “box” style casing as the capacitor is encased is a flame retardant or flame-proof case.

There are two types of Safety Capacitors

X Capacitor: Capacitor for use in situations where failure would not lead to danger of electric shock. This is also known as a line to line application.

Y Capacitor: Capacitor for use in situations where failure could lead to danger of electric shock. This is also known as a line to ground application.

X rated capacitors are of two types

X1  Type

Rated voltage 250 V AC

Withstanding voltage 1500V AC 60 Hz

Impulse Voltage 4000V

X2 Type

Rated voltage 250 V AC

Withstanding voltage 1500V AC 60 Hz

Impulse Voltage 2500V

The purpose of these capacitors is to reduce radio frequency interference and to ensure safety from shock and fire. These are generally used in circuits where alternating, pulsating, intermittent and high steady voltage exists.