Raspberry Pi Zero Repair – Checking for 1.8 V

If you have a dead Raspberry Pi Zero, then this multi-page article might help with repairs, however you need to begin from the first page in the sequence. In this section, we check if the 1.8 V is present.

As you can see from the circuit diagram, PAM2306AYPKE establishes the 1.8 V rail through pin 2 (LX2). This channel is also on a soft start delay as the enable pin 12 (EN2) reaches threshold voltage slowly as C2 charges. As you can imagine, C2 charges very slowly through R1, which is 100 kΩ in value and 1 % tolerance. This gives all the other doodads such as the GPIO interface, SD Memory, and camera, on the 3.3 V rail a head start as they place a greater load requirement. Soft start is one of the nicer power management features of this IC because it limits the in-rush current prevalent at start-up. It does this by switching the input current in small steps to the maximum that the load requires. This has the advantage of preventing voltage drops at the input and thereby deep drain of the battery.

Checking for 1.8 V

With your multimeter set to measure DC voltages, connect the black probe to test point PP5, and the red probe to test point PP9. If the voltage is missing or abnormally low, then you will need to isolate pin 2 and investigate further as before. If the 1.8 V returns after isolation of pin 2, then another IC connected to that rail is short. Alternatively, if the voltage remains missing, then PAM2306AYPKE requires replacing.

Replacing PAM2306AYPKE

Replacing the PAM2306AYPKE dc-dc step-down converter is a simple job if you are experienced working with small components. You will very likely require a microscope for this task. Note that there are different versions of the PAM 2306 IC and the letters in the suffix determine the type. The last two letters "K" and "E" signify the output voltages; therefore, you should get the precise replacement.

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