🔋💻 IBM 16V 72W Laptop Charger
 
(16V 4.5A AC Adapter • 72W • 5.5 mm × 2.5 mm Barrel Connector • No Center Pin)

This classic AC adapter delivers 72W of regulated DC power to IBM ThinkPads using the 5.5 mm × 2.5 mm barrel connector. It was the standard supply for the T‑, X‑, R‑, and A‑series ThinkPads of the late 1990s and early 2000s.
 
🔧 Charger Form
Input: 100–240V AC, 50/60Hz
Output: 16V DC, 4.5A (72W)
Connector: 5.5 mm outer / 2.5 mm inner barrel, no center pin
Inline power brick with detachable AC cord
Often labeled as 02K6549, 02K6550, 02K6551, or equivalent
 
🖥️ Compatible Devices
🖤 ThinkPad T‑Series
T20, T21, T22, T23
T30
T40, T40p, T41, T41p, T42, T42p, T43
🖤 ThinkPad X‑Series
X20, X21, X22, X23, X24
X30, X31, X32
X40
🖤 ThinkPad R‑Series
R30, R31, R32
R40, R40e
R50, R51, R52
🖤 ThinkPad A‑Series
A20, A21, A22, A30, A31
🖤 ThinkPad S‑Series
S30, S31
🖤 Other IBM Models
i‑Series (i1200, i1300, i1500)
Select early ThinkPad i‑Series and E‑Series notebooks
 
✅ Common Uses
🔌 Powering IBM ThinkPads with Pentium III / Pentium M CPUs
🧩 Replacing lost or damaged OEM 72W adapters
🏢 Standardizing spares for legacy ThinkPad fleets
🎒 Keeping as a travel adapter for vintage collectors
🧪 Testing IBM laptops with a known‑good 72W supply
 
🧠 Signal Format
⚡ Input: Universal AC (100–240V)
🔋 Output: Regulated 16V DC, 72W max
🔌 No center pin — relies on barrel contact only
🔁 Backward compatible with lower‑power 56W ThinkPads (safe, charges faster)
 
⚠️ Things to Watch Out For
📉 Not suitable for Lenovo slim‑tip or USB‑C ThinkPads
🔌 Connector must match — not interchangeable with later Lenovo barrels
🧯 Avoid third‑party clones with poor contact — may cause intermittent charging
🌀 Excess heat or frayed cables can cause power dropouts
🧪 Always confirm laptop’s required wattage before swapping adapters
 
🛠️ Quick Tips for Beginners
🧭 Check underside of ThinkPad or original charger for voltage and connector size
🔌 Use only with laptops rated for 16V and 72W barrel input
🧪 If laptop reports “adapter not recognized,” inspect barrel contact and cable integrity
🧯 Label adapters clearly to avoid mix‑ups with Lenovo slim‑tip chargers
🧵 Keep one at desk and one in travel bag for convenience