[FERNSEH]

Late production BRC 1590 sets employed a silicon transistor as the replacement for the AU113. In fact the later PCBs were fitted with links to allow this.
The NPN silicon transistor was wired "upside down", that is,with the collector to ground. A type BD160 comes to mind.
The BRC 1612 mono TV of 1974 employed modern silicon transistors so the power supply line was positive. According to the circuit diagram a PNP line output transistor was employed. The transistor VT8 was wired into the circuit with the collector to ground, again, upside down.

The attachment shows the circuit arrangement in the 1612 chassis when a PNP line output transistor is employed. I'd consider something like this for the TT1.

DFWB.