Hi,
for a long time, I had a faulty 820-1889-A Macbook, a fried donated to me. Today I decided to fix it. I knew, that it had a blown backlight fuse, but now the Macbook didn’t turn on at all. So I took the logic board out of the Macbook. The Charger Light was green, but it sometimes disappeared but there was no fan spin.
Well, I had a schematic for this board but no board view. So I decided to try the first obvious thing: testing the voltage of the backup / bios battery. I measured about 2.8V without Charger. After I plugged the charger in, the voltage dropped to 2.6V.
So the battery was bad, but I had no other by the hand. So I decided to use my Lab-Power Supply to put 3V on this “rail”. So I took a crocodile clamp and put it on the Firewire port and connected it to the not grounded minus port of the power supply. The plus I connected to a small probe. The probe was just on the table, not on the board.
I was setting the voltage on the power supply without turning the output on, in this moment I heard a strange sound. In the moment I looked to the board and saw, that the fan was spinning and just in this moment the magic smoke escaped from the NH82801GBM Hub.
I don’t understand, what went wrong and why I have blown the Hub. I’ve just connected one wire of the power supply (not the cheap china power supplys, but a Rigol DP832A 800$ supply). Do you have any idea, what went wrong?
for a long time, I had a faulty 820-1889-A Macbook, a fried donated to me. Today I decided to fix it. I knew, that it had a blown backlight fuse, but now the Macbook didn’t turn on at all. So I took the logic board out of the Macbook. The Charger Light was green, but it sometimes disappeared but there was no fan spin.
Well, I had a schematic for this board but no board view. So I decided to try the first obvious thing: testing the voltage of the backup / bios battery. I measured about 2.8V without Charger. After I plugged the charger in, the voltage dropped to 2.6V.
So the battery was bad, but I had no other by the hand. So I decided to use my Lab-Power Supply to put 3V on this “rail”. So I took a crocodile clamp and put it on the Firewire port and connected it to the not grounded minus port of the power supply. The plus I connected to a small probe. The probe was just on the table, not on the board.
I was setting the voltage on the power supply without turning the output on, in this moment I heard a strange sound. In the moment I looked to the board and saw, that the fan was spinning and just in this moment the magic smoke escaped from the NH82801GBM Hub.
I don’t understand, what went wrong and why I have blown the Hub. I’ve just connected one wire of the power supply (not the cheap china power supplys, but a Rigol DP832A 800$ supply). Do you have any idea, what went wrong?