1708 No USB power after U1 replacement

[Andrunin]

Here is another puzzle.


I replaced the USB Port because it made a bad connection and checked continuity between the plug of a cable and the components on the port. All seems ok with the USB port.


U1, D23 and the trace near U1p3 were all scorched. I replaced U1, D23 and ran a jumper from p3 to L2. The board works ok with batteries, but has no power with USB.

I can measure 5V at C7, but nothing at pin3. On a good board I get 3V there. I did this repair on 3 boards with the same problem, but it worked only on one board. What could it be? Is it a bad U1 chip?












These are from a job lot for repairs, but turned out it was a box of junk where the seller assembles the devices with components that he couldn't repair.. I managed to fix most of them so far but they were incredibly hard to fix. Good thing is I learned so much from trying to fix these

[RDC]

7 of those 8 pins on that chip make connection to the PCB, so you need to make sure they all are and that no pad/trace was torched and broke making an open there.

Also need to check the Resistors there (R16, R17, R18) to make sure they haven't gone open or out of spec.

1 - NC, but measures ~4.5v
2 - USB 5v
3 - 3v
4 - GND
5 - 3v
6 - GND
7 - 0.6v
8 - ~4.5v

[Andrunin]

Ah yes thanks a lot. I had a cold solder joint at pin 8 in both cases and now they work. I'm still quite new to this stuff and not sure what my mistake was. I used hot air and a lot of flux for these components.

Just one more question. In one case I didn't have the exact same model for the diode D23 because I ran out of them from donor boards. I used one with a A2 R2 marking instead of 2D. It has a higher voltage drop of 0.6V instead of 0.2V. It works fine anyway from what I can tell. Do you think that's going to be lasting repair or should I get the correct one?

[wickated]

low drop diode - shottki

[RDC]

It'll be fine in that case as it's not in any type of switching circuit. There's no reason at all for it to be a Schottky as the USB 5v - 0.6 = 4.4v to the input of U1, well above the 3v output it generates. It'll be a shade less efficient, but that's all.

[wickated]

It'll be fine in that case as it's not in any type of switching circuit. There's no reason at all for it to be a Schottky as the USB 5v - 0.6 = 4.4v to the input of U1, well above the 3v output it generates. It'll be a shade less efficient, but that's all.

and also most of diodes on xbox controllers are reversed - from ground to line, which mean they are for protection