Ripped off connector with no trace left

connectoridentification

My friend's phone (ZTE F101) had the miniUSB connector ripped of the board, and when it broke it also pulled the pad. All 5 pads of the connector don't have traces and instead they have micro-vias right in the middle to the inner layers.
We don't care about the USB connectivity, but without the connector the phone can't be recharged, so we are trying to restore the GND and the +5V pins of the connector ignoring D+ and D-. The ground connection was easy to restore by simply connecting it to the ground plane available everywhere, but can't figure out where to connect the +5V.

I found an interesting spot on the other side of the board (relative to the miniUSB connector) where there is a big cap with one end connected to ground, and the other connected to a possibly SOT23-3 diode (marked with "S 5") as seen in the second picture, which made me believe that's where all the juice goes. So I connected to that cap, my little jumper wire connected to the +5V from the miniUSB connector, but it didn't work. The phone does not indicate that is charging the battery.

Does anyone have any idea what else to try, or recognize any voltage regulators in the picture?

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Best Answer

The only things I can advise in this are as follows:

  1. Try to see if the original micro-via still contains sufficient metallisation to measure with a multimeter.
  2. Find a place where the resistance to that micro-via is as good as zero.
  3. Test with a lab supply by touching the micro via with +5V while measuring the voltage on that pad (if it's not a mentionable drop, it might work).

Noting that:

  • Maybe you can still solder to the micro-via, although its connection to the inner layer may be damaged and create a higher than advisable resistance.
  • Usually the +5V goes directly to a power management chip with passives surrounding it (coils and caps) to control both charge and the power flow to the electronics.
  • You may have already broken something by willy-nilly forcing 5V on some part that may have been meant to create a low-drop 1.8V, or even lower.
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