I have aquired a Gibson G-80 chassis and a schematic. The amp hums and shuts off and hums and shuts off. I examined the schematic and there was a difference in the Chip in the input channel. the schematic shows a Motorola MC1303L and the actual chassis has a Motorola SC17063L. I am having a hard time finding any parts as this was built in 1971. I would like to replace the IC's and output transistors. does anyone have a good source to obselete parts? some has probably tried to exchange the chip at some point. The PCB is clean and all the parts look good (not burnt) If someone has one would post some layouts or other pics. I would appreciate it! This amp was made in three flavors in the output section mine is the TIP version (TIP 29C,TIP 30C,and TIP 33B. I would like to build this into a Head version it was a 4x10 combo amp. All help is appreciated, thanks !