The Tektronix 015-0073-00 is an accessory power supply providing +12.5 V and -12.5 V at 150 mA each. It is intended for probes, e.g. the P6045.
The 015-0073-00 uses a mains frequency (non-SMPS) transformer, with separate secondaries for the +12.5 V supply and the -12.5 V supply.
Both supplies are regulated independently with zener diodes. The regulators use MPS6521 NPN bipolar transistors as error amplifiers. The regulator output is a Darlington pair formed by a MPS6515 and a RCA40250.