Jean,
The quick answer is that there is usually an easy DIY repair that should cost you nothing.
The usual fault is a shorted 12V TVS diode at location D4 on the PCB. The simple solution is to cut it out with flush cutters. However, before taking any drastic action, obtain a digital multimeter and take some measurements.
Set your multimeter on the 200 ohms range and measure the resistances of both components. Also measure D3 and R67.
R64 and R67 should measure close to 0 ohms. If either is open, then bridge it with a wire link or blob of solder. If either D4 or D3 measures close to 0 ohms, then it is shorted, in which case cut it out with flush cutters. The drive will work OK without it, but it will no longer have overvoltage protection on the affected supply. Be absolutely sure your PSU is OK.
If, for continued protection, you wish to replace the diode, then a 5V TVS diode can be substituted with an SMAJ5.0A, and a 12V diode with an SMBJ12A. They can be ordered from Farnell, Mouser, Digikey.
If you need help identifying the components, upload a detailed photo or scan of the component side of the PCB.