r/electronic_circuits • u/Gabrymost01 • 8d ago

On topic Key not working (Xbox360)

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I recently bought this Keyboard, made exclusively for the videogame Rockband 3. This is the Xbox 360 version.

Every key works normally, except for the up arrow of the D-pad (the top left key in the first picture).

I tried disassembling it and cleaning the contact with alcohol, but nothing changed. The circuit looks intact to me, I don't know why this key still's not working.

Is there something else I can try?

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2

u/Amazing_Actuary_5241 8d ago

Have you tried swapping the dome with a known working one?

1

u/Gabrymost01 8d ago

Yep, didn't work

1

u/Amazing_Actuary_5241 8d ago edited 8d ago

Looking at the PCB you're gonna have to trace the pad and find the next component in the path (looks to be D1). A quick glance at the board suggests to me the board is designed as a key matrix array and that D1 diode seems to be the one for the up arrow. Using a multimeter test the diode for forward and reverse operation.

Edit: typo.

0

u/Gabrymost01 8d ago

I don't have a multimeter. Actually I don't know anything about circuits, but I understood what you're saying. Do you think D8 is only linked to the up arrow? If D8 doesn't work, shouldn't every other key linked to it not work?

1

u/Amazing_Actuary_5241 8d ago

I apologize, I confused the up arrow with the Y button (looked right instead of left). For the up arrow on the left it should be D1 not D8. Same principle just different component.

Because the buttons are arranged in a button matrix configuration each button has a unique diode to control what's known in keyboards as ghost keys. So those diodes each regulates one button.

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u/Gabrymost01 8d ago

I see, so it probably is D1, I guess? I still don't know what I can do 😅

1

u/Amazing_Actuary_5241 8d ago

The repair requires testing the component to identify if its faulty and then re-soldering a replacement part. Without the tools or skills to perform either you'll have to bring it to a shop for diagnosis and repairs.

1

u/1Davide 8d ago

Get a meter. With the power off, start measuring continuity wen you press the dome.