Variable Isolation Transformer And Safety Analyz
Many electronic devices that operate from the AC line do not have an isolation transformer. Some of these chassis have one side of the AC line connected directly to the chassis. Other devices use a full-wave bridge rectifier connected to the chassis which places the chassis at one-half the line voltage no matter how the line cord is connected to the AC line. These chassis must be isolated from the common side of the AC line with an isolation transformer to prevent shock hazards and to prevent the possibility of damaging the device under test or test equipment connected directly to the chassis.
Many new circuit troubleshooting procedures require that the AC line voltage be adjustable to test regulators, shut-down circuits, and other voltage sensitive circuits. Increasing or reducing the line voltage can also help locate intermittent problems that do not show up with 117 volts applied to the input.
The ability to monitor the current or power drawn from the AC line often simplifies troubleshooting of Power supply
or power output stage problems. Abnormally high power consumption indicates a problem that may not be immediately recognized but which may cause problems in the future.
Finally, every unit serviced should be checked to make sure that exposed metal parts do not pose a shock hazard to the user. A safety test is recommended by all manufacturers. This test is often not done because the procedures given in service literature are difficult to perform and interpret.
AC POWERITE™ is an AC safety supply designed to make sure that every factor related to power is correct. The operation is simplified and all of the features needed to meet these needs are included in a single, compact instrument.
The Sencore PR57
POWERITE™ features four functions in one compact package. First, the PR57
has an isolation transformer to isolate chassis that have one side connected directly to the AC power line to eliminate shock hazards during service. The isolation transformer also provides safety for the test equipment and prevents possible damage to the set itself.
Second, the PR57
has a variable AC transformer that allows you to vary the isolated AC output voltage from 0 to 140 volts AC. You can apply a high and low line to check regulator and shut down circuit operation or apply a high line to cook out that intermittent trouble.
Third, the PR57
meter lets you monitor the AC line voltage or the AC voltage from the isolated output. The meter also allows you to monitor the wattage and current being drawn by the unit under test. The PR57
meter lets you know when the voltage and power are right.
Fourth, the PR57
provides a safety leakage test so you can check each customer's set for AC line leakage as recommended by most manufacturers. There is no external resistors or meters to hook up with the PR57
, Simply depress a button, touch the exposed metal parts with the Safety Leakage Test Probe
and read the leakage current on the meter.
PO WE RITE™ also features a magnetic circuit breaker backed up by a 4 Amp slo-blo fuse. The PR57
is protected, even from a direct short on the isolated output. The PR57
also has only one isolated output to prevent plugging in more than one unit and defeating the isolation of the isolation transformer and creating a potential shock hazard.