The Sepura 300-00384 is a 12 bay charger for the Sepura STP series of Tetra Radios. It has 6 bays for charging of loose batteries, and 6 bays for direct charging of a radio with battery.
Problem
Someone has spilled water in one of the charging slots, or inserted a very wet battery for charging. The charging slot is defective. This model of charger is not very rugged despite its extortionate price of around 850USD (not including the power cable of all things). It has a layer of conformal coating on the PCBs, but the chassis is made of a very cheap type of plastic. According to the markings the electronics is made by a company called Powersolve Electronics Ltd.But all things being equal, I manage four of these, and all of them has survived several years of rugged gear-destroying search and rescue volunteers without issue so far, so they must have done something right.
Analysis
The green death and its preceding cousin white water damage was detected upon inspection of the battery connector. One of the pins has also been bent out of shape, and the black carbonation left on it indicates that it has created a short circuit at some point.
Some disassembly is in order to inspect the rest of the board. The charger is held together by a million screws hidden under some of the abundant rubber feet. That is, there are screws hidden under all the rubber feet, but only some of them can be removed at this stage so do not bother removing all of the rubber feet. The red arrows on the picture below points at the screws you need to remove to be able to take off the bottom plate. They are standard PH2 coarse thread screws for plastics, the type you will find in most cheap and some expensive electronic devices.
The screws located underneath the rubber feet not removed above cannot be unscrewed until you have removed the bottom plate.
The charging electronics is split onto seven circuit boards. Six charging circuits, each controlling one battery slot and one radio slot, and one power distribution board (PDB). To remove and inspect our defective slot board we have to loosen the power distribution board and remove the screws holding the charging board. There is a power cable connecting each charging board to the PDB, and it is accessible underneath the PDB when you lift it slightly. Disconnect the power cable BEFORE you remove the charging module. The cable has a connector in both ends, and I found that disconnecting the PDB-end was easiest.
I disconnected all of the power cables to inspect the PDB for damage on both sides.
Closer inspection of the faulty module reveals water ingress beyond the externally exposed pins and what looks like the remains of a short circuit arcing in addition to what could be detected from the outside. The pins were shorted due to the buildup of green death.
Repair
- The green death was removed using electronics cleaner (any quick evaporating type will do), some q-tips and a the reverse of a small knife/scalpel. Be careful not to damage the conformal coating.
- The carbon deposits on the pin were removed with a scalpel and a small flat-head screwdriver.
- Some small square-head pliers were used to straighten out the bent pin and make it look like the others. Most small lightweight pliers for electronics use should work, but avoids using large radio pliers as you could easily destroy the pins.
- The arc damage was polished off with electronics cleaner and a lint free cloth.
- A small dab of Fluid Film NAS was added to the base of the pins to prevent any further corrosion.
Assembly and testing
Be careful not to bend any of the pins when re-inserting the charging module. Remember you have five pins in total, three battery pins and two radio pins at the other end of the board.
The image above shows the charger during final testing. Both the battery and radio slots are working properly now.