My adapter cable was frayed(close to the adapter side), sometimes it wouldn't charge. So I was trying to fix it. I didn't buy a new cable for replacement, instead I cut the original one and soldered on the circuit board.
But after I repaired it, I connected both sides of the adapter to my MacBook Air and to the power socket see if it worked. I saw the indicator lights up and then turns off immediately. After few times plugged and unplugged, I twice got a successful charge connection; the indicator turned green and then turns orange but it won't last longer than 5 minutes. After a while the indicator will turn off again. These two charges got my MacBook 13% power.
I measured the the T connector positive pins(Pin2/4); sometimes I got 0.8V, sometimes it showed 0.5v, I also measured the backside of circuit with multi-meter(yellow and red circle); the voltage showed was 110VDC. I think this adapter probably still working just don't know where I did it wrong.
Please give me some advice on what to do next to get this working.
03/26 Thanks for you guys reply. I was trying to measure voltage by the pin in the green circle, I got 55VDC, but suddenly there was a spark and then the voltage here were all gone, so I checked from the top and saw 3 SMD resistors next to this chip(green circle) were burned... I am thinking to replace them because it still recognizable. But except that, I don't see any blown capacitor that might cause no charging. Would someone please share some advice?