หัวอ่านแม่เหล็กของเครื่องอ่านบัตร ATM: NCR, Diebold, Wincor และ Hyosung — คู่มือความเข้ากันได้

An ATM card reader is a deceptively simple subsystem: a magnetic head reads (and on some models writes) the three tracks of magnetic stripe data as a card is fed past it, while a feed-roller assembly transports the card. Of the dozens of failure modes a field tech encounters, three quarters trace back to the magnetic head — wear from repeated card passes, contamination from dust and adhesive residue, or end-of-life coil degradation.

The magnetic head itself contains tiny coils (one per track — three for full-coverage readers) wound around ferrite cores. As the cardholder dips and the magnetic stripe passes the head, the changing magnetic field induces a small voltage in the coils; the controller amplifies and decodes that signal back into ASCII track data.

Heads come in two electrical flavours that look identical to the eye:

• LoCo (low-coercivity), read-only. Reads standard 300 oersted magnetic stripes. Cheaper. Used in older deposit-only or balance-only ATMs.
• HiCo (high-coercivity), read & write. Reads and re-writes 2,750 oersted stripes — the standard for modern bank-issued cards. Required for any ATM that updates the magnetic stripe (rare today) or for closed-loop loyalty / transit cards. The right default for any modern install.

The four ATM brands that dominate the global installed base — NCR, Diebold (now Diebold Nixdorf), Wincor (now part of Diebold Nixdorf), and Hyosung — all source their magnetic head assemblies from a small upstream OEM pool. The visible end-product is branded differently, but the head itself is often physically identical.

The single biggest time-saver when ordering replacements is knowing which OEM part numbers map onto the same upstream physical assembly. The interchange table below covers the most common dip-reader heads — independently confirmed across ATMParts.net and ATMHeads.com cross-references and decades of field swaps.

Before assuming the head, run these field-proven checks — they take 5 minutes and eliminate the most common false positives:

The aftermarket for ATM card-reader heads has wide quality variance — from tier-1 manufacturers selling the same upstream assembly under their own brand, to unbranded heads with mismatched coercivity that look identical in product photos. The four-question screen below catches the vast majority of bad listings:

1. What is the OEM part-number cross-reference? A good supplier publishes this without being asked. If they can't tell you which Wincor / NCR / Diebold part it replaces, walk away.
2. HiCo or LoCo? The default for any modern bank ATM is HiCo. Suppliers who can't immediately answer haven't tested the part.
3. What is the resistance (Ω) per track? Quality suppliers test and specify this. It's the diagnostic for counterfeit heads — the real OEM spec is published in service manuals.
4. Warranty period and return policy? Reputable aftermarket heads carry 6–12 months. “No returns” or “sold as-is” is a red flag.