Electro Harmonix Bassballs vintage 1978 burned

[AleBass78]

Hello everybody.
I am trying to repair the pedal in question. The owner reversed the polarity of the power supply and burned it. I noticed that one of the two transistors is burned and I can't read the number. I need your help: do you know what the type is? Do you have schematic of this vintage model (1978)?
Thaks a lot!
Alessandro