After the successful receiver fix, my friend asked if I could look at his headphones. They are JBL LIVE 400BT headphones. They appear to have no power. I took them apart, here are the photos.
The charging board where the micro USB charger plugs into
![](https://cdn.badcaps-static.com/image_cache/bbd0c72e6bca27db102883cb5d2b2082.jpg)
Main board where the power switch and other buttons are
![](https://cdn.badcaps-static.com/image_cache/282af3250a40aec2db2ad815cad7a7b8.jpg)
The other side of that board
![](https://cdn.badcaps-static.com/image_cache/c8a4be95412270a18ea833ec5d1c5081.jpg)
First I plugged it in, and I was getting 4.2V from the USB connector. I checked the battery terminals and they were getting 4.2V as well. After some time I unplugged the USB connector, and the batter was still reading 4.2 volts, so the battery looks to be charging and good. During this charging time, none of the LED's lit up and the device does not turn on.
I checked the wires connecting the smaller charging board with the main board for continuity. All the wires checked out, so it's not a break in a wire anywhere.
I checked for voltage on the main board between VBAT and GND, and was getting 4.17 volts. I checked VBAT to the far side of that row of components and all but one of them showed around 4 volts, one was around 2 volts, I can't recall which one.
I checked voltage to the pads that were near the power switch, all showed 4.17 volts. Throughout all the testing the headphones showed no life whatsoever.
Any tips on what components to check? I wouldn't think I could be reading power all over the place yet the device would be absolutely dead. I'm not seeing traces where I would usually suspect so it's hard to "follow the voltage" and see whats going where
The charging board where the micro USB charger plugs into
![](https://cdn.badcaps-static.com/image_cache/bbd0c72e6bca27db102883cb5d2b2082.jpg)
Main board where the power switch and other buttons are
![](https://cdn.badcaps-static.com/image_cache/282af3250a40aec2db2ad815cad7a7b8.jpg)
The other side of that board
![](https://cdn.badcaps-static.com/image_cache/c8a4be95412270a18ea833ec5d1c5081.jpg)
First I plugged it in, and I was getting 4.2V from the USB connector. I checked the battery terminals and they were getting 4.2V as well. After some time I unplugged the USB connector, and the batter was still reading 4.2 volts, so the battery looks to be charging and good. During this charging time, none of the LED's lit up and the device does not turn on.
I checked the wires connecting the smaller charging board with the main board for continuity. All the wires checked out, so it's not a break in a wire anywhere.
I checked for voltage on the main board between VBAT and GND, and was getting 4.17 volts. I checked VBAT to the far side of that row of components and all but one of them showed around 4 volts, one was around 2 volts, I can't recall which one.
I checked voltage to the pads that were near the power switch, all showed 4.17 volts. Throughout all the testing the headphones showed no life whatsoever.
Any tips on what components to check? I wouldn't think I could be reading power all over the place yet the device would be absolutely dead. I'm not seeing traces where I would usually suspect so it's hard to "follow the voltage" and see whats going where
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