This charger failed after a few charges & i decided it was not worth a 300Km trip to get money back on the warranty ( there was probably no chargers in stock any way) Opened it up & found one of a pair of 200V 5A shottkey diodes, one was shorted (they are in parallel) So having some 200V 8A shottkey diodes lying around i replace both of them, & it now works fine. So some times you can have a winner.

 

There seems some irony that electronic items more likely to fail are also, frequently, easier to repair than those with more reliable and sophisticated designs.

I have a Bosch charger that sits disassembled waiting for me to bother going past the quick assessment I first gave it. I would probably be more motivated if not for the fact that I have, literally, 10 working ones, three of which sit on the shelf in reserve.

Very nice to hear of a repair success. I find repair one of the most satisfying technical activities because it feels like rescuing value.

 

Nice one, what is on the heatsink and underneath the pcb?

 

Theres a MOSFET on the heat sink for the switch mode supply. Other side of board has surface mount components & driver chip. If they were faulty i probably would have not bothered to repair it. What i find interesting is even with a short on the power supply, it just shut down with the overload & not destroy its self.

 

What chip is it, that's why I asked for a picture..?

 

Will dismantle it & take picture.

 

I was all set to jump in and say, "it's a capacitor", but I guess these things have other failure modes.

I've taken apart maybe a half-dozen or more SMPS bricks from various appliances and they have ALL failed due to a high voltage capacitor failure.

The old-fashioned wall-warts that they replaced occasionally failed if they had rectifying diodes, but almost never because of the transformer. The SMPS was introduced to replace the "more wasteful" wall-wart but I wonder, with the wisdom of hindsight, if that was the right decision. I believe building all those replacement SMPSs and sending all the dead ones to the dump is probably worse for the environment than the tiny vampire current of long-lasting wall warts. Anybody ever see data on this?

 

The IC 1 is QBUA, thats all thats on the chip, i suspect its a custom made drive chip & its small. The CM4N60 power MOSFET is 600V 4A. IC3 is 78L05 reg. IC4 is LM358 dual op amp.IC5 has no markings but does drive the 2 indicator LEDS. If any of these parts had failed i would have binned it.