hi there, i'm fixing a car amp .. and i just change the transistors IRFZ34.. in the CASE say SEC 818 IRFZ34A and i just replace it for a normal IRFZ34.. when i turn on the amplifier the fuses BLOW!!! why is that.. ??is any difference beetwen SEC 818 irfz34a and irfz34..?? thanks... (i from VENEZUELA)