Today we'll be looking at a CENTECH heavy duty battery charger from the Bug ranch. They Generally brake in the same fashion and can be repaired cheaply. I will attempt to the greatest extent possible, troubleshoot without power. This device can be lethal so precautions should be taken. This device is Harbor Freight number 63043.

For demonstrations of failure I will be using a Variac and an isolation transformer for safety. After which power off troubleshooting commences. With the checking of switches, and resistance through the fan and coil. Note that as I apply power at intervals its only for demonstration.

With the rectifier disconnected the hum is gone and the fan spins at full voltage.Showing the problem is from the rectifiers back. Setting the Fluke Meter to Diode, all rectifiers are tested, in both directions finding immediate issues, notably shorts found.

10MM Button Diodes, 50 Amp, 400 Volt (PRV), TinPlated Contacts, Solder Connection (10 Pack)
https://amzn.to/42pouY3

The entire Diode panel is remove from the unit. Damage is evident so the rivets are drilled out and the diode housing is removed. The housing on the effected diode is melted requiring an minor repair. The plate is cleaned and the prepared for reassembly. While epoxy dries in the recess on the housing from the melting. New diodes will be used all around, 10MM 50 Amp, I purchased from Power Forged PN 69604010. All of the diodes are tested in the bag, finding the closest characteristics, then reassembled into the housings. The housing were riveted, now secured with machine screws and nuts.

After testing, the whole diode board is reinstalled into the unit, all wires reconnected. Testing will be done live with a Variac and isolation at low ac voltage. Everything looking good so all of the functions will be checked, along with the devices voltmeter. Now at full voltage everything is retested and the unladen numbers look good. A final test is done under load charging a battery. Everything looking good, and a significant drop in AC ripple as expected. A successful repair.


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