Repairing Your ODROID-N2: How To Recover From An Accidental Short Circuit

In this guide we will show you how to repair Q1 on your ODROID-N2. The original article was taken from the Hardkernel wiki page available here: https://wiki.odroid.com/odroid-n2/hardware/repairs

Figure 1 - Discrete Load Switch Schematic with FTK3407

Causes of Q1 Transistor Failure

Over-currents, even for a short duration, can cause progressive damage to a MOSFET, often with little noticeable temperature rise before failure. MOSFETs often carry a high peak-current rating, but these ratings typically assume peak currents only lasting 300 µsec or so. And cumulative over-current may cause damage.

The causes of Q1 failure are generally from built-in current limiting circuits in integrated power switches to prevent the load SW from being destroyed during over-currents. In the case of discrete load SW, the current limiting circuit is not built in, so the P-CH FET FTK3407 is damaged due to over-currents as shown above.

When the eMMC is mounted to reverse, over-current flows to VCC3V3 due to the FLASH_1V8 node short circuit to GND.
GPIO connection error or GPIO short-circuit on the 40-pin IO port.

Failure to function -- due to failure

As shown below, the load switch does not supply the VCC3V3 node due to damage and its power supply is not supplied, so booting to the eMMC, USB, Ethernet and IO pin etc. does not work.

Figure 2 - Block diagram of MOSFET that is damaged

Repair procedure

Note:

You can also replace AO3407A alternatively since FTK3470 is not easily accessible.
Make sure to leave the components R44, R45, and C147 nearby Q1 alone. Small parts could go flying by your wayward soldering iron.

Step 1. Basically, you could see the Q1 damaged by its appearance as shown in figure 3.

Step 2. To easily detach Q1, you should add a little solder on the pad of Q1.

Figure 4 - Solder added to Q1 for easier removal

Step 3. If you have a spare soldering iron, use it as shown in the image. If you don't have a spare soldering iron, it will be harder than using a single soldering iron, but you could try melting solder on the three pads at the same time and then pull part out.

Figure 5 - Using 2 soldering irons to remove Q1, heating all of the pads at the same time

Step 4. Remove the rest of the solder on the pad. Use a solder wick for solder removal.

Figure 7 - Copper wick used to remove any residual solder

Step 5. Use SMD tweezers and soldering the new Q1 into place.

Figure 9 - New MOSFET held in place with tweezers

Conclusion

We hope that this guide helped you with repairing your ODROID-N2. After replacing Q1 (P-CH FET), your USB, Ethernet, Expansion Connector 3.3V power, and eMMC booting should work perfectly.