see para two first. If not successful,
Seems to be smps power supply and will be costly.
You can take the defective unit to an Electronic shop, and ask ,
replacement with input
Ac 230V~ and output ,( if possible
regulated at 10 V= DC . current rating should be 1AMP
Be careful about connect plug. Inner +ve etc.
Cost will be around Rs 200/=
Don't buy cordless Power adapters as current rating is very low.
Para two;
try in BSNL for a replacement.
If modem purchased outright within a year replacement
possible. . ( purchased in Feb 2009)
Take both adapter and modem to Exchange for testing.