2A charger

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Official specifications:

I got this charger from fasttech

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A very simple and compact design.



Measurements


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The idle voltage is a bit high, but drops into range when charger is loaded. The 2A specification is very optimistic, 0.75A looks much more realistic.

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The charger has no problem sustaining the 0.75A load for one hour.
The temperature photos below are taken between 30 minutes and 60 minutes into the 1 hour test.

Temp1660

M1: 43,5C, M2: 42,1C, HS1: 63,0C

The charger gets warm, but nothing serious.

Temp1661

M1: 52,8C, M2: 42,6C, HS1: 60,4C

Temp1662

M1: 51,4C, HS1: 52,9C

6.5ohm

There is a lot of noise 120mV rms and 1000mVpp.

10ohm

Even at lower current there is lot of noise 120mV rms and 950mVpp.



Tear down

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Pressing on the charger with a vice and the bottom pops open.

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Two circuit boards with a flatcable between, expirence says this is very bad design.

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The white paper on the trafo is used to improve isolation.

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Both mains input (AC1 & AC2) and usb output are on the same circuit board and with very little safety distance.
The resistor at AC2 is the fuse, then we have a rectifier bridge and C1 is the mains capacitor. The SMD capacitor beyond C1 is placed between the mains and low volt side, it is supposed to be a safety capacitor, but is not.

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There are many places with way to short isolation distance (Distance between mains and low volt side must be over 6 mm on a circuit board). One place is the flat cable, blue is low volt side and red is mains, distance is less than 1mm.


The charger failed a isolation test with 2500 volt, this makes it doubtful to use with 120VAC mains. The fail made a short between mains and low voltage side (Very bad)!



Conclusion

Another cheap charger with very bad safety, stay away.




Notes

Index of all tested USB power supplies/chargers
Read more about how I test USB power supplies/charger