PowerBright Inverter Fault Smoking Capacitor Failure

The green arrows indicate the capacitors that I replaced to cure the fault.

You'll need a CP4750HTT 47uF/50V and two CP220025HTT 2200uF/25V from click HERE

I bought the "Power Bright APS300-12 Pure Sine Power Inverter 300 Watt 12 Volt DC To 110 Volt AC " on 07/15/2010 from Amazon.com

I needed it to run my office computer system during periods of power outage. I mounted it in a plastic box in a shady area outside the office, with two 6V 200AH batteries and two battery chargers (also from Amazon). A fan was installed to draw warm air out of the box.

Yesterday October 4, 2011 my computers died. I checked outside and smoke was pouring from the inverter. The LED was flickering red/green alternately. I switched it off and disconnected it.

To dismantle it you must remove the four black screws at each end then lift out the L-section yellow metal cover.

Remove the silver screws in the black heatsink and the little steel brackets inside, which clamp the transistors to the grey heat-conductive silicone insulator sheet.

Remove the 5 silver screws holding the PCB (printed circuit board) to the base.

To remove the faulty capacitors, you'll need a VERY hot tip soldering iron (at least 400 °C) and desoldering braid such as "solder wick".

Click HERE for soldering instructions.

I could see that the top of one of the capacitors was bulging slightly - a sure sign of internal pressure, indicating total failure. When I turned the PCB upside down I could see a hole burnt around one of the capacitor leads, indicated by the arrow in the photo below.

I cut away the carbonised portion of the PCB. Luckily, it didn't need repair because the copper land was still intact and there was enough strength around it. If it had needed repair, I would have used epoxy resin with glass fibres, and solder braid to reinforce the copper land.

Conclusion: in my opinion, the original capacitors were unfit for purpose and early failure was inevitable. (In my case they lasted for exactly 12 months.) The capacitors that I used to replace them have a very low ESR (effective series resistance) and should last for several more years.

I think I was very lucky to have been present at the time of failure, otherwise the inverter might have been damaged beyond repair. My advice to anyone owning one is to replace these capacitors BEFORE they fail.

You'll need a CP4750HTT 47uF/50V and two CP220025HTT 2200uF/25V from click HERE

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