This behavior is often caused by bad electrolytic capacitors on the circuit board inside. It's not difficult to replace them, but requires skill with electronic soldering and access to the replacement parts. This site
as well as some others has information showing what needs to be done, and detailing the parts to be replaced.
If you know someone who can solder, give it a try. There are many online parts sources, and if you live near a Radio Shack store, you might be able to find the replacement capacitors there. A capacitor's value is measured in microfarads, usually abbreviated as MF. There is also a voltage rating. The original parts are rated at 16 volts; if 25- or 35-volt rated ones of the same value are available, use those. They will be a little larger than the originals, but will last longer.
Good luck with the repair, and thanks for using Fixya!