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G4 Gigabit Ethernet Bodge Diodes?
Posted by: John8520 on 2018-04-05 09:39:25
Was poking around with my GigE G4 earlier today and I happened to notice something interesting on the voltage regulator near the ADC power connector, VR1500. It looks like two diodes in series, soldered back to back, on pins two and three. Anyone see this before?

2018-04-05_12_35_48.jpg

Posted by: Andropov on 2018-04-05 12:46:37
Ah, I've seen something similar on a G4 Cube logic board (not, mine, it was posted on another forum). It was this thread. The images were online less than a week ago, but not anymore... I've searched in case I had downloaded the image but no luck. Still, I remember them looking exactly the same and the colours of the diodes/current regulators mentioned in that thread match yours.

EDIT: Aha! I found the wrong thread, although it mentioned the same thing, so it might be a somewhat common modification. The thread I was referring originally was this one. As you can see, the soldered components look exactly the same as yours.

EDIT2: I have also noticed that some ICs on the logic board picture of the second thread are different than those on my Cube. In the second thread someone says:

There are other board that got "hacked" like that. They think it was done by Apple on first-fun boards.

http://www.cubeowner.com/forums/index.php?s=&showtopic=10029&view=findpost&p=66499http://www.cubeowner.com/forums/index.php?showtopic=11556&st=0&p=75893&#entry75893
That seems consistent with my findings (the logic board differs from mine, which was manufactured well into the Cube's life).

About the specific electrical reasons behind soldering those, I don't know. In the case of the Cube, both ICs are LMJ2679 but the other label differ from JM03AB to JM05DV. The datasheet is here, but it doesn't mention different versions.

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