Part identification keyboard pcb

Semiconductor Discrete Semiconductor Products
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I’m trying to fix a Corsair mechanical keyboard but could someone tell me what the circled part is as I think it may be the issue. There is 2 legs with a small square see through piece at the top that is separated inside almost like a fuse but it’s labeled d140 which I assume is some type of diode?. I tried searching but couldn’t find any part that looks like this.

IMG_6981
IMG_69811920×1441 630 KB

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Usually diodes in a clear housing are either a photodiode or LED.

2 Likes
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Hi @ntec ,

As @PaulHutch suggested, that is definitely an LED. You can (in most cases) safely remove it to see if your problem gets resolved (If not, explain what you are seeing).

Cheers, heke

4

Thanks, I do see now that it is an led. The problem is the keyboard is not recognized and there is no sign of life with no keycap led’s lit up. I tested the connector where the cable plugs into pcb and there is 5v coming in. I also tested the caps and resistors and there doesn’t appear to be any shorts.

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Hi @ntec ,

Probably the LEDs are controlled by the keyboard MCU. It sounds like the MCU (or whatever controller the keyboard is using) does not boot up, as you do not have any connectivity. There are a few things you could try. But, first, if possible, could you post a photo of the keyboard (the portion containing the electronics, that is).

Cheers, heke

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IMG_6996
IMG_69961920×1440 686 KB

IMG_6985
IMG_69851920×1440 993 KB

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Hi @ntec ,

Thanks for the photos.

I wonder, could you measure the voltage at each pin of Q1 component (3 pins), as well as for Q11. Also voltages at capacitors C6 and C7.

The controller MC9C08 takes it’s supply from USB port, thus there is a risk that the controller is dead (e.g. due to supply transient). In that case you’ll be out of luck, as the firmware is stored to the controller’s flash memory. Merely replacing the chip won’t suffice.

Cheers, heke

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Q1 and Q11 0 volts from the side the has 1 leg and 5 volts from one of the legs on the side that has 2 legs. I am also getting 0 volts from C6 and C7.

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Hi @ntec ,

Thanks. Sounds good. Probably the Q1 has gone south.

I wonder, can you take a closer up photo of the Q1? Need to see the marking.

Cheers, heke

1 Like
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Here is the marking.

IMG_6998
IMG_69981920×2560 596 KB

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Hi @ntec ,

Thanks for the pic.

It looks like you’ll need to replace that guy. Could not find exact type based on the marking, but is likely a power P-MOSFET.

You could try similar, such as this

https://www.digikey.com/en/products/detail/onsemi/FDN302P/413230

Cheers, heke

1 Like
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Thanks for all your help, I have ordered the mosfets and see if it fixes it before I scrap the keyboard.