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I have this Philips One Blade trimmer (disassembly video) and I have probably by mistake tried to charge it with charger from the older Phillips shaver which had almost identical connector but 15V instead of 4.3V used by this one - the result is it can't charge. I opened it and there is one burned component on the PCB, but I can't identify what is it (I am not much of electronics expert).

I would be glad for help with identifying that component or a replacement alternative to repair the trimmer.

Solution summary: The part was diod in SOD323 package. I replaced it with 1N4148WS-SOD323 and it seems to work. Thanks for all help.

PCB Photo

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The 'A' and 'K' markings suggest a diode, probably installed for reverse poalrity protection.

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  • \$\begingroup\$ Thanks. So the diode would have anode on Ch+ (which is + from the charging power supply) and cathode on the B+ which is the + of the battery (given the power supply is 4.3V and battery is 1.2V NiMh). Would that make sense? \$\endgroup\$ – Michal Mar 21 '20 at 15:08
  • \$\begingroup\$ Yes. @user245763 suggestion is a good one. Remove the diode, check for shorts with a multimeter. If there are any, something else is wrong. \$\endgroup\$ – polwel Mar 21 '20 at 16:10
  • \$\begingroup\$ I sourced several SMD diodes with packages which could roughly match. It the SOD232 package seemed to fit the best. With diode 1N4148WS-SOD323 the trimmer seems to both charge and work. \$\endgroup\$ – Michal Mar 24 '20 at 18:48
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@polwel i agree most likely a diode for RPP incase connection is reversed on entry, check for continuity or very low resistance to ground on both sides of the pad with a multimeter

if its not shorted to ground then any or even no (but bad idea) diode will do

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  • \$\begingroup\$ I'm not sure if "any" diode will do, you want one with a low forward voltage drop. Using a 3.3V battery and a 1v Vf diode won't leave much left for the circuit to operate. Less important in this circuit is the current handling capability, but you don't want to have a 100mA diode when the circuit pulls 500mA during operation. \$\endgroup\$ – Ron Beyer Mar 21 '20 at 17:11
  • \$\begingroup\$ @user245763 It was not shorted to the ground. So I tried to replace the diode with a wire, which resulted in battery charging with 1.4V (per DC multimeter). However, the motor did not start. So I removed the wire and now it works. I now have time till next charging to determine and source the right diode. \$\endgroup\$ – Michal Mar 21 '20 at 21:00
  • \$\begingroup\$ @RonBeyer The battery is 1.2 NiMh. The charger is rated 4.3V/70mA - and the diode is between charger+ and battery+. So you would suggest a diode with low voltage drop and current higher than 70m (so let's say 200 to be safe)? \$\endgroup\$ – Michal Mar 21 '20 at 21:05

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