Electronics > Repair
Percul gokart laptimer repair and teardown
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adinsen:
What I thought was a P-channel MOSFET turned out to be more. I removed the component from the board as it was clearly not providing power. Underneath it was the number "5520". It took me some research, but I eventually found the device: R5520 are power switches for USB applications.

There are two different versions of it, R5520H001A and R5520H001B the only difference being the polarity of the EN-signal that turns on the switch. The one fitted by Percul is the A-version that switches on with a 0V input signal. For further testing, I've replaced it with a wire link as shown in the picture. Unfortunately Mouser only stocks the B-version and I haven't been able to find other sources of the A-version. I've not yet searched eBay.

As can be seen there are now signs of life again. It doesn't react on button presses, though. Pressing the buttons convert to voltage between 0 and 1V depending on what button is pressed. I've traced this signal to an analogue input on the MCU. With the clock generator running at the right frequency the CPU must be running, so why is it not reacting in the display?  :-BROKE

I'll have to do some more tracing...

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