Have a look at the number on that, er, "transistor".
I'll guess that it shows something like "7808" or "7809", or "78M09".
Or maybe "LM340".
More than once when the two-transistor regulator fails in a radio with a EPT6900 pc board we save the labor of fixing the original circuit by bolting in a one-piece 3-terminal regulator. Looks like a transistor until you read the type number.
Does the same job, and also has a current limit built into it. Fooling around with the echo board, or taking loose a board bolted to the side rail can short the 9-Volt supply to ground and blow out the factory regulator.
It's a PITA to troubleshoot the factory circuit, but the 3-terminal part will fix the problem quickly and be more reliable in the long run.
Pinout of the new regulator chip calls for some "crossed legs" to get the proper hookup.
73