Check also UF3 and UF4. Check also UD4. Check also UF4 and UE4. Check also UF3 and UE4. LED dim, flickers, or does not come on at all.
Drive appears dead, but spindle motor runs continuously.
May be intermittant and fail after warmup. This part normally runs hot and is a common failure item. Drive appears to power up normally, but motors do not run. Otherwise, only CR3 will get hot. For example, note how the drive motors and indicator LED's function when the drive is powered up, reset, and accessed by the computer.