Last night my T43 made the beep sound (same sound when you connect/disconnect power supply) and since then its not charging the laptop. The laptop is working fine on the battery power. When searching for the problem I cam across this thread and someone mentioned a fusible link. Can someone please tell me where that circuit is located.

From Other Thread:
A bad battery or charging circuit may be attempting to pull too much current. Remove all batteries and see what happens. In fact, remove all removable devices (drives, mouse, PC Cards, USB, etc.) - just to eliminate them from the equation.

If batteries, charging circuit and the DC power supply is good, then this is usually caused by a broken or worn power connector in the notebook, or a "thermistor" or "fusible link" inside the notebook that blew, for some reason. The "for some reason" is the tricky part. Thermistors and fusible links are circuit breaker type safety devices designed to sacrifice themselves by burning up, thus "opening" the circuits they are protecting from abnormal power (high-current) conditions.

Visually inspect the notebook's power connector under a bright light to see if damaged. If you are certain there is no visible damage (bent pins, signs of smoke or excessive heat, cracked plastic, etc.) connect the power pack and gently wiggle around the plug to see if connection is made - strategic positioning of tongue is often necessary.

If a fusible link blew, the tricky part is determining why did it blow? Did it fail prematurely on it's own? They do - they are not very high-tech or expensive. Was it just a fluke? Gremlins? Can the link be replaced and everything will be okay? Or is there something else wrong in the notebook, a short somewhere that is causing too big of a current flow in the circuit? If the safety device blew because it overheated due to too much current draw through the circuit, then replacing the link will simply result in the new link blowing, hopefully before further damage elsewhere occurs.

In either case, if it is the connector, or something else internal to the notebook, it will need to go into a good shop. Replacing power connectors and thermistors/fusible links is a relatively simple task for a qualified repair person - disassembly to access the parts and re-assembly takes longer than actually removing and soldering in new components. The parts, are inexpensive and should not take more than one hour of labor.

However, if the fusible-link failed "as designed" because something else failed, then troubleshooting may take some time and replacement parts may be expensive. You may have to decide between fixing or replacing the entire notebook.