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remove nearly all of the remaining ripple. (See the waveform for point 8, which shows almost no visible
ripple.) You now have almost pure dc.
No matter what power supplies you use in the future, they all do the same thing—they change ac
voltage into dc voltage.
Component Problems
The following paragraphs will give you an indication of troubles that occur with many different
electronic circuit components.
TRANSFORMER AND CHOKE TROUBLES.—As you should know by now, the transformer
and the choke are quite similar in construction. Likewise, the basic troubles that they may develop are
comparable.
1. A winding can open.
2. Two or more turns of one winding can short together.
3. A winding can short to the casing, which is usually grounded.
4. Two windings (primary and secondary) can short together. This trouble is possible, of course,
only in transformers.
When you have decided which of these four possible troubles could be causing the symptoms, you
have definite steps to take. If you surmise that there is an open winding, or windings shorted together or
to ground, an ohmmeter continuity check will locate the trouble. If the turns of a winding are shorted
together, you may not be able to detect a difference in winding resistance. Therefore, you need to connect
a good transformer in the place of the old one and see if the symptoms are eliminated. Keep in mind that
transformers are difficult to replace. Make absolutely sure that the trouble is not elsewhere in the circuit
before you change the transformer.
Occasionally, the shorts will only appear when the operating voltages are applied to the transformer.
In this case you might find the trouble with a megger-an instrument which applies a high voltage as it
reads resistance.
CAPACITOR AND RESISTOR TROUBLES.—Just two things can happen to a capacitor:
1. It may open up, removing the capacitor completely from the circuit.
2. It may develop an internal short circuit. This means that it begins to pass current as though it were
a resistor or a direct short.
