Looking for a replacement part; need help finding from photo
There are a bunch of schematics for Fender amps online, I found this as a likely candidate.

The device is likely a TIP142 with the "TI" burned off.

Add: Since that's the device you need to heed some warnings in trying to repair the amp. 


The TIP142/147 are Darlington pairs and in this amplifier are operated in Class A-B. This means they get quite warm with no output (they typically dissipate about 2-3 W at idle).
Check the diodes CR42-CR45. If one of these is open (or a bad soldered joint) you will blow your replacement device.
If you have EE skills I'd suggest that you break the op amp output signal from the final stage and check the op amp is ok. If you don't understand what I just said, then replace the MC1436 as well as the TIP142.