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How do I test the backlight circuit?

So I don't know if I should buy this but I probably will. It is a iPod touch 4 with no backlights. As far as I know, it had no water damage. Where would I test things on the board? Any backlight filters, fuses, diodes, etc. I should check?

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The iPod Touch's are difficult to troubleshoot at a board level because there are no known schematics (if someone has them, please share a link!).

That said, I'm certain the circuit is very similar, if not identical, to the iPhone 3GS/iPhone 4. You just need to figure out where on the logic board these parts located. Always start with the filter, then diode, then coil, then driver IC.

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Do you know which one is the filter?

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Sorry, no. That's my point, with no schematic I can't tell you for certain. Look at the schematic of the 3GS/4 and see what the IC is for the backlight circuit. It's probably the same IC for the Touch. The coil, diode and filter are usually right next to it.

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