José, welcome to Beoworld !
If we are talking about the output stage transistors, they are type 2N5034 and long out of production.
Finding new 2N5034 transistors is impossible. You may be able to find modern substitutes with the same specs
but it's an old transistor with a very unique housing (seen with modern eyes) so no modern transistors
will fit physically.
However, I may be able to supply a pair of original transistors, used and tested if you need.
Your repairer should also replace (and readjust) the idle current trimmers and the DC supply voltage
trimmer on the same board. They will most likely have oxidized to a point where they are about to fall apart.
There's a handful of electrolytic capacitors too plus the large one at the right end of the board. After 40 years
they will most likely need repalcing too. They are not costly components so easily worth replacing.
Martin