I finally got the transistors needed to repair the driver board for the amplifier. Using TIP41C and TIP42C as replacements for the original transistors at location Q5LR and Q6LR worked fine, they are even pin compatible and fitted straight in at the PCB. With the new transistors I had sound at both channels, but there was a loud hum at the repaired one when not playing a record. I replaced all three electrolytic capacitors at the board and it got dead quiet. Since the capacitors at the driver board for the other channel are of the same age I changed also those to make sure not having to revisit the juke box to change them later on.
