MagSafe puzzle! 820-00164-A (green light and not a green light)

[KC Micro Tronix]

I cut the wires off of chargers and use them in my bench top supply similar to what Louis Rossmann does. I even use the same old HP power power-supplies he does. I ran into a board that gave me a spanking and wanted to see what people's thoughts on this would be.

I serviced this laptop and fixed water damage which was minor. After repairing the water damage I tested it with my bench top power supply. I clicked the mag safe, got the green light and fin spin. The board passed diagnostics. I was happy. wrapped it up and moved on.

The machine came back the next day and the fault was "no green light on the charger" I tested it once again and it worked perfect. Green light every time. I performed cold tests, hot tests and flexing and every time it worked. So... i sent it back as good.

It came back again!!!! I checked it again and it was good so I took it back to the depot and checked it there with their charger and No green light! WTF.. so I took it back to the bench and tested it with a plain charger not my power supply. Guess what.. No green light!

How can it give me a green light with my bench supply and refuse to green light a standard charger?

I understand that my charger sends the 18.5V regardless of the green light but if the SMC talks properly to my cord the light turns green.

Has anyone seen this? I don't even know where to start. I already changed the SMC!

 

[2informaticos]

You must understand (more times explained here), original Apple charger is (very) smart.
It detects leakage and will not provide power to the board.
Usually Q7180 issue, but D7012 can generate same issue.

Magsafe 2 charger provides 3V in the first moment; magsafe 1 has 6V output instead.
If embedded processor detects a proper machine connected, then full output voltage is enabled.
Bench power supply always delivers the adjusted output voltage!

 

[JohnB8812]

You MUST use OEM 85 watt MagSafe 1 and 2 chargers. Bench power supply is not the best idea imo

 

[KC Micro Tronix]

Q7180 WOW........

I use the 85w charger cable. I cut it off a 85w head. I don't think I can give up the bench power supply. It gives me such quick and accurate information. Often I can diagnose the problem by just looking at the supply before I open up the machine. I have however started double checking boards with the regular power adapter as part of my QA. This was the first time I had seen this fault. Totally caught me off guard.

 

[2informaticos]

"I don't think I can give up the bench power supply."
How do you plan to find next leakage issue then???

Apart of that, connecting cable from bench power supply a bit angled, high voltage will touch ADAPTER_SENSE pin; many times ending with dead SMC!

Bench power supply helps, but must be VERY CAREFULLY using it.
Is better to connect positive output AFTER cable is connected to the board in test.

 

[KC Micro Tronix]

I can't give it up. I could connect the laptop before hitting "enter" on the power supply to be careful. I have to watch it's power consumption and feel it. I guess I could get a AC amp meter for the AC adapter and watch that instead? I have to see what the machine is consuming. There is no way around that. That information is so valuable. Watching power consumption while watching thermal explains so much to how the machine boots and in what order. There is no way I can give up the bench power. I would feel blind.

Even if I have to get out my stencil and replace a SMC now and then it's worth it. I have been on bench power for 6 months now and have not blown a SMC. I have sparked the plug so many times. Got it on side ways, The plug looks scary. But it still works.. When it dies I will just harvest another one.