Android TV Box power supply repair

An easy fix for a supply that wasn't outputting any power.
Aug 08, 2020 — 5 mins read — Electronics

Android TV Box power supply repair

I was given this Android TV Box to repair it and the complaint was that it won’t turn on. 

As an additional symptom, I was told that several times in the past, the cable had to be wiggled close to the power jack for the box to turn on so I knew that the fault was either in the power jack on the Android box or in the power supply cable. 

To diagnose the Android box and its power supply port, I had a similar charger available and I used it to power on the box and it worked as expected. With this, I knew that the issue is with the charger so I moved my focus to it. 

To start the charger inspection, I plugged it into the AC outlet and I measured the voltage on its output. This is a 5V power supply and I definitely was not getting 5V but only some fluctuations of a few hundred millivolts.

This confirmed my suspicion that the power supply is faulty so I proceeded into opening it and inspecting the fault. 

Unfortunately, the power supply enclosure was not easy to be opened. It did not have any screws on the outside as it was pressed fitted and then glued together.  

To open it, I used a flat head screwdriver in combination with a utility knife to break the glue connection on the joint and to pry open the two halves.

Depending on the manufacturer and the type of glue that they use, this opening process can be very difficult and in some cases, it might even be just a one-way endeavor and the case can get damaged so badly that it won’t be able to be put back together. 

Luckily for me, the glue released quite quickly, so I break open the case and I removed the circuit board from the inside. 

The output cable was soldered on the board and the AC connection was made through two pins that were pressed in the soldered slots. This is a common construction so the case can be split opened if needed. 

Now with the board extracted, I first made a visual inspection of it, looking for any obvious issues like bulging capacitors, any burning marks, broken connections, or similar but everything looked OK. 

To test out the output cable, I switched my multimeter to continuity mode and I checked the connections on both of the leads going to the power jack. As I expected, I only got continuity on the positive connection but not on the negative wire. 

This explains the small fluctuations that we saw earlier when we tried the charger connected to the wall as only the positive voltage was connected and some induced floating voltage was measured. 

To verify that the charger circuit was indeed working as expected, I had to try it out while being out of the case so I used alligator clips and an AC cable with exposed wires to connect the charger PCB to 220V. 

Please be careful when doing things like this! AC is deadly and can easily kill you if you are not careful. To protect the leads and me from accidentally touching any of the live wires, I used a piece of electrical tape to isolate the leads.

While still being very careful, I measured the voltage on the two points where the output cable was soldered to the board and I was able to measure the full output voltage as rated on the power supply of 5V. This meant that the PCB was functionally and only the cable was the issue. 

Since a broken connection on the power jack is very common, I wanted to check and see if this was the case so I cut a piece of the output wire at a few centimeters from the jack and exposed its copper. 

I used my multimeter again to check for continuity and this time, both of the wires showed good connections with the PCB. I thought that I’ve probably cut away the bad section of the cable so I removed the jack from the piece that leftover and stripped the molded plastic from around it. 

This exposed its contacts and with a bit of solder, I soldered the wires back to it making sure to keep the same polarity where the positive wire is connected to the center and the negative to the outer contact of the power jack. 

When that was done, I’ve put together the two halves of the power supply and I connected it to the wall to test it out. To my surprise, the output voltage was still a few hundred millivolts and I knew that the cable had to be changed entirely. 

I checked my cables bin and I found one that was almost the same as the one on the power supply. I opened the case once again and using my soldering iron, I first removed the old wire, I stripped the ends of the new one and I soldered it in place.

The same process was repeated on the other side, where I first removed the jack from the end of the old cable, stripped the wires on the new cable and soldered the jack to the new cable. 

I then press fitted the case of the power supply and connected it to the wall so I can test it out. This time, the voltage was correct at 5V and the supply was back in business. 

To finish off the repair and secure the case, I used a bit of hot glue that I’ve applied it where the cable exits from the supply case, I’ve molded a handle out of hot glue to the DC jack to protect the connections and I’ve added a bit of hot glue to the case as well so it stays secure. 

Let me know down in the comments if you have any questions or suggestions, be sure to like the video, subscribe for more videos and I’ll see you all in the next one. 

Tools and materials used in the video:

Replacement parts:

tv reuse basic electronics power supply repair tutorial charger
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