Abstract: A preamplifier for a multi-head disk drive includes a circuit that tests the connectivity of each magnetic head in the disk drive by driving each head with a small current, and detecting the flow of this current. By driving and sensing the current flowing through the magnetic heads, both open-circuit faults and bridging faults can be detected. In a preferred embodiment, each head is tested sequentially. The result of each test is stored as a bit value in a register, for subsequent access. The circuit may be activated by a test device, or by a microcontroller in an assembled disk drive. To minimize costs, the circuit is integral to the circuitry that is conventionally used to read and write information via the magnetic heads. The oscillator that is conventionally used to characterize the read heads of a disk drive is used in a preferred embodiment to control the sequencing of tests through each head.