Disassembly Nokia Phone Charger acp-7x

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Disassembly Nokia Phone Charger acp-7x. Sometimes I use this to charge small RC toy cars I find in charity shops as the out is stated as 3.7 volts 355 mA. Sometimes it works and sometime it damages the car. Today I decided to measure the outputs and have a look inside. It is a simple transformer with 4 diodes acting as a rectifier bridge. The ‘no load’ output voltage is just short of 9 volts so I would suggest using a DC-DC buck converter to stabilise the output if you considered doing the…

9 Comments on "Disassembly Nokia Phone Charger acp-7x"

  1. Hi,
    Thanks for your detail sharing this video. May I know where did you buy the special screw driver head? and what the detail spec? I face this problem when I tried to open Nokia adapter which has the same screws on it. It would be appreciated for your help. Frank Chang

  2. Switching trasformator?

  3. It turns out, these chargers are actually 7.6v, not 3.7v. I found the service manual for these Nokia phones, and it lists the ACP-7 as a 7.6v charger.. Contrary to what they say. Not sure how they got UL listed with an error like that on the bricks, but it seems they all have this mistake.

  4. Nokia ain't daft, they must have designed it to do what they wanted. Low cost electronics sometimes includes invisible really clever features. The current could be limited by the thermistor, or there could be a gap in the transformer, that's a good way of adding inductance and controlling current. I'd suggest briefly measuring the short circuit current, or the current into a LiPo, with the meter on its 10A range and the test leads in the appropriate sockets.

  5. Interesting that you call the third prong Earth, I have always heard it referred to as Ground. Do most non-Americans say Earth?

  6. Under load I'd be willing to bet the voltage drops off near the rated output, say 4.2? There may be further regulation in the phone it was designed to be used with.

  7. Always enjoy these, even though I don't really understand electrics, it's still interesting.

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