Sounds like the EZ-B main board (bottom board) has been damaged. If the top board (comm board) was damaged, the speaker would inform of a communication error. Instead, the bottom board is not responding - also, there is no red led which means the bottom board main chip is damaged.

Find out more by clicking here: https://synthiam.com/Tutorials/FAQ.aspx#10

You can either replace the bottom board, or replace the entire ez-b v4.

The bottom board can be damaged by a few ways.

1. static charge is an enemy of electronics. The ez-b v4 took over a year of development and has been designed to withstand as much static charge via grounding and isolation resistors on the signal pins. The ez-b v4 has additional hardware that you will not find on any other micro controller which protects against static charge. However, even with all these preventions, there are still incidents where static will damage the controller. Because this occurrence is rare and also incredibly random, it's difficult to diagnose and isolate an incident responsible.

2. Shorting the pins accidentantly. We all make mistakes, and sometimes the power pin is shorted against a signal pin accidentally. This can happen if connecting a servo or sensor and the pins bend and connect. Or this can happen if a screw driver touches the pins. Or even if any conductive surface touches the ez-b v4 pins briefly. All servos and sensors use the same power pin arrangement of Ground, Voltage, Signal (GVS for short). This arrangement puts the power pin in the center of the two, which means it can short either way. If it shorts to GND, the fuse will blow. If it shorts to Signal, the EZ-B main controller will blow.

DJ, thank you so much for the explanation. Clearly some incident (my fault mad ) damaged the main board. I will order a new main board and see what happens. Hope it does not take too long to get one because I was really starting to enjoy the product and discovering its great potential. I will surely be extra careful next time ! Thanks again for your help