Logitech mx ergo wireless trackball mouse

on the PCB are several components marked with z1, z2, etc. The components are 1.77mm x 1.18mm x 0.79mm. There are two lines on the silk screening. The top line says “AZ” and the bottom says “H5”. There are small dimples on each component, which i assume are the cathode since they match white lines on the PCB that are on one side of each ‘z’ component. The lithium battery in the mouse is 3.7v and most of the components that come back from a google search for “H5” show zener diodes with higher voltages like 9v and 6v.

Hello and thank you for posting on our TechForum.

What questions do you have on that PCB and if you could share some images that would also be helpful.

pictured is the source PCB with a component missing, the traces leading to a breakout board with two switches on it. I had desoldered another component from lower on the board to run tests on. So far it’s not acting like anything. I put an LCR meter on it and it’s showing 5pf at 200kHz, it shows 1.45 G ohms either direction, when i put a diode tester on it it says 6.8v either direction. I have no idea what it is because it’s not behaving like anything i know of.

A bidirectional TVS diode may exhibit such behaviors; when the applied test voltage is below the breakdown threshold, they will appear to be slightly capacitive with a high leakage resistance; apply a larger test voltage and the breakdown voltage may be observed. Bidirectional devices exhibit such behaviors more or less symmetrically. They are commonly used as protection against static discharge when external signals connect to a board, as appears to be the likely case for placements Z6,7 illustrated above.

The given measurements would appear consistent with an SOD323 package, and a 6.8V breakdown would be a likely choice for a system designed to operate from 5v logic.

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