It happens. Electronics fail; parts wear out. Like a light bulb, sometimes they don't last long at all - other times they last forever!
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“A” connects to the display panel:
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Troubleshooting:
If the BATM won’t turn on, the following items should be checked:
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Items outlined in green are necessary for the BATM to turn on.
The coreboard is required, as well as the power supply barrel connection and 2 display cables.
Items outline in red are attached to other peripherals that may be causing an issue.
A defective item attached to the mainboard may prevent it from booting properly.
Disconnect peripherals when attempting to determine if the mainboard is at fault.
If the issue remains after those cables have been disconnected, then the coreboard and/or mainboard may be defective. Further troubleshooting is required.