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Example: the meter reading displayed in Figure 8 indicates this transformer has an output of
90.9 volts AC. This is within the range of 83 to 97 volts anticipated, thus this transformer is
good.
Charger DC voltage
rating
AC volt output with a good
capacitor
AC volt output with capacitor
disconnected
36
83 to 97
55 to 65
If the transformer secondary coil voltage measures between 55-65, either the capacitor coil on
the transformer may be open, the capacitor coil terminals are not making proper contact or the
capacitor may be open. The influence of the capacitor on transformer AC output is significant -
- consider the loss of more than 30 volts when it is not connected as in this example. You
would find the effect on DC output to be even greater. Typically if a capacitor is disconnected
or has failed, the actual current output while charging is near zero. Please refer to “Capacitor
Testing” Item 10, for further details.
DANGER: RISK OF ELECTRIC SHOCK! HIGH VOLTAGE! THE VOLTAGE AT THE
CAPACITOR TERMINALS CAN BE AS HIGH AS 660 VOLTS WHILE THE CHARGER
OPERATES. USE EXTREME CAUTION WHEN YOU ARE NEAR THE CAPACITOR
TERMINALS.
To test the transformer capacitor coil to check if it is open, remove the AC input cord from its
outlet and the DC output plug from the battery receptacle. Discharge the capacitor by
adjusting your test meter to its highest DC voltage scale and then touch and hold the test leads
to the capacitor terminals for three seconds. Follow this by ‘shorting’ across the terminals with
an insulated metal tool. A capacitor discharged in this manner will be safe to touch.
Carefully remove one of the quick disconnect female terminals from the capacitor. Use a large
needle nose-pliers or similar clamping tool that you feel comfortably in control of and grasp the
body of the quick disconnect terminal to remove it. Do NOT pull directly on the copper wire or
a broken connection can occur. With a multi-meter set to measure resistance on the lowest
scale, measure across the transformer coil wires. The value should be less than 0.02 ohms. If
the meter measures open, the transformer capacitor coil is open or is making a bad contact to
the terminal. If it should become necessary to replace a terminal on one of the transformer
leads, the new terminal must be crimped and soldered.
9.
DIODE ASSEMBLY TESTING
The purpose of this test is to confirm if a diode is good or bad. A diode
is a semi-conductor
device that behaves as an electrical ‘one-way’ check valve that allows electrical current to flow
in only one direction. A good
diode will have ‘continuity’ and measurable resistance in one
direction of polarity and no ‘continuity’ or measurable resistance when the polarity is reversed.
A
failed diode will measure ‘shorted’ (continuity), or ‘open’ (no continuity), in both directions of
polarity.
CAUTION: DISCONNECT BOTH AC INPUT AND DC OUTPUT CORDS FROM ALL
POWER SOURCES. POWER IS NOT NEEDED FOR THIS TEST.
