Bad capacitor on M5-1 mouse
The PCB pictured is from an IBM Model M keyboard, specifically a M5-1 made in 1993. The M5-1 has a small trackball mouse just above the cursor keys. This board is for the mouse. The keyboard's mouse recently quit working, so I took it apart to diagnose the problem. I think the capacitor pictured (center; metal cylinder) has failed based on what looks like corrosion on the board below the capacitor. They can leak, and the leakage damages the board.
On the other side of the board is the largest attached chip. It is probably the processor that implements getting the mouse input and making it available to a computer system using the PS/2 protocol. When this board is connected to the other board in the keyboard, the clock and data lines for the mouse are held low. Given the protocol, that is a sensible thing to do while the processor isn't yet ready to communicate, but it never changes. The bad capacitor may be the cause.
Bad capacitor on M5-1 mouse
The PCB pictured is from an IBM Model M keyboard, specifically a M5-1 made in 1993. The M5-1 has a small trackball mouse just above the cursor keys. This board is for the mouse. The keyboard's mouse recently quit working, so I took it apart to diagnose the problem. I think the capacitor pictured (center; metal cylinder) has failed based on what looks like corrosion on the board below the capacitor. They can leak, and the leakage damages the board.
On the other side of the board is the largest attached chip. It is probably the processor that implements getting the mouse input and making it available to a computer system using the PS/2 protocol. When this board is connected to the other board in the keyboard, the clock and data lines for the mouse are held low. Given the protocol, that is a sensible thing to do while the processor isn't yet ready to communicate, but it never changes. The bad capacitor may be the cause.