Image: Raspberry Pi Model B+ V1.2 (2014) (Click on image for larger view.)
I own a Raspberry Pi Model B+ V1.2 manufactured in 2014. In 2024 I noticed that if I plug a USB Sound Card Adapter in any of the ports it would not recognize the adapter. None of the four USB Ports were working! I noticed that the green led was blinking and that component U13, gets abnormally hot. The Ethernet port is working fine. U13 was identified as a AP2553 a single channel precision adjustable current-limited switch. I needed to find a solution or the PI would become a static ornament against the wall in my shack. After searching the Internet I had the following options to solve the issue:
1. Replace the "faulty" AP2553 with a new one.
2. Modify (bypass) the AP2553 to solve the problem.
3. Check the Power Supply that it puts out enough voltage and amps.
4. Check capacitor C97 and if faulty replace it.
Well you guess correctly I started fault finding with the easiest option to check capacitor C97. I used a multi-meter. While the Pi is Off, try using the buzzer of the multi-meter and check the 2 pins of C97. If you hear the beep sound then the problem is with the capacitor, remove it from the PCB and check it again. If it beep again then C97 is toast. This was the case with capacitor C97 in my Pi. The next step was to check the voltage and amps of the power supply. It was more than adequate and there was no red flickering led or messages that there is a power problem. I then decided to first check if removing C97 solved my USB issue. Low and behold the USB ports came back to life after removing C97. Thankfully the AP2553 was not damaged and all four USB ports are now working again. I need not replace the AP2553 or do the bypass modification to solve my issue. I will install a new capacitor at C97 and hopefully use this Raspberry Pi still for many years to come.
Herewith the links I used:
1. https://forums.raspberrypi.com/viewtopic.php?t=110164
2. https://forums.raspberrypi.com/viewtopic.php?f=28&t=162103
Images: (Click on images for larger view.)
