Page 9 - Testing Electronic Components

4. Isolation Transformer

When servicing any electronic equipment, always use an isolation
transformer to protect yourself from an electrical shock. During servicing,
the isolation transformer is connected between the equipment and ac
power line. An isolation transformer is a transformer that has a 1:1 turn
ratio to provide the standard line voltage at the secondary outlet. This
means that it does not change the voltage. The transformer still produces
240V AC at its outputs, but both sides of this AC lines are independent of
ground. If you were to accidentally touch one of these outputs, you would
be protected. The isolation transformer must be rated to handle the power
of any equipment connected to it. Typical ratings are 250 to 500W.

Note: A variable transformer or variacs is not an isolation transformer.

5. Discharging the Cathode Ray Tube (CRT) Anode

The CRT of a Monitor and TV can hold a dangerous charge, even if the
Monitor and TV have not been used several days. All CRT have graphite
coating on the internal and external surfaces of the glass bell. This
conductive graphite coating are commonly known as aquadag coating and
it forms the two plates of a high voltage filter capacitor using the glass in

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