I posted about adding heatsink to the pre-driver modules in the Yamaha forum. Basically the failure point in the pre driver is one transistor. Inside these module you basically have surface mount technology. If you get a TO-220 heatsink, about 3/4" x 3/" with fins sticking up, and use some JB Weld to glue it to the metal back of the pre driver, it goes a long way to preserving them. Looking at the rear (metal side) of the module locate the heatsink about 1/2" from the top and from the left side.