Printed Circuit Board # 4

AWA Capacitor DC Leakage Tester PCB

Price:  $25 including shipping to USA addresses

Bare Board

Board Populated

Front

Rear

This bare printed circuit board (PCB) can serve as a component of a capacitor DC leakage tester and capacitor former.  This printed circuit board component and the resulting Capacitor DC Leakage Tester are intended for experienced persons. The completed unit and associated components produce potentially dangerous voltages.

A capacitor DC leakage tester that utilizes the populated PCB develops a test voltage that is adjustable over the nominal range 10 to 600 volts DC.  It uses a dual primary transformer, which can be configured for 120 or 240 volt AC operation.  To measure leakage current, a digital multimeter or accurate 20 kiloohms/volt VOM can be used to monitor the voltage across a resistor in series with the ground end of the capacitor under test.   The meter scale is then 1 volt equals 1 milliampere of leakage.  Provision is also made for monitoring the charge/discharge voltage across the capacitor under test using a DMM or VOM.  By using two meters simultaneously, one can monitor both applied voltage and leakage current as the voltage is increased.

The bare PCB ships with a representative wiring diagram and parts list with Mouser part numbers.  The cost of the additional components is currently about $30, not including an enclosure, line cord, fuse, on/off switch and hookup wire.

Here are a few safety items to review and understand before purchasing this PCB:

Do not charge a capacitor with higher voltage than its specified rating. Doing so may permanently damage the capacitor, and may generate gas or heat inside the capacitor, resulting in swelling, fire or bursting.

Do not reverse placement of (+) and (-). Many capacitors, particularly electrolytic filter capacitors, have polarity. If the (+) and (-) leads of the capacitor are reverse-connected to the tester, it may cause a short-circuit or over-current discharge of the capacitor, and may result in overheating, explosion, fire or damage to the tester.

Capacitors can remain energized for long periods.  A capacitor can hold a potentially dangerous electrical charge for a prolonged time, and should always be discharged after testing or otherwise energizing.

It is strongly suggested that the device be mounted in a metal enclosure, grounded through a three-wire AC line cord.

Here is a testing procedure that we use:

1.  Always start with the test voltage control at minimum and the test switch in the DISCHARGE position.

2.  Using an ohmmeter, check the capacitor to be tested to rule out obviously shorted components.

3.  Connect the capacitor under test, taking care to ensure that proper polarity is observed.

4.  Turn AC power ON and observe the charge voltage meter to ensure it is reading zero.

5.  Place the test switch in the TEST position and slowly increase the test voltage control while observing the voltage and current meters. 

6.  Ensure that the voltage rating of the capacitor under test is not exceeded by monitoring the charge voltage meter. Do not exceed 10 mA of charge current for extended periods of time.

7.  When the rated capacitor voltage is reached and capacitor current stabilizes, you can read the leakage current on the monitor meter; the scale is 1 v equals 1 ma.  For large value capacitors, this process may take a while.

8.  To disconnect the capacitor under test, return the voltage control to minimum and place the test switch in the DISCHARGE position.  Observe the voltage indicated on the voltage monitor and do not attempt to remove the capacitor until it has been completely discharged.

9.  Do not leave the tester unattended.

To make your purchase (US only shipping in price, check for non-US shipping below) go to AWA Store here.

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