Does Transformer heating add noise to a circuit?
OK, you have 20VAC from the transformer, which is then full-bridge rectified to give (1.414*20) - (0.7*2)=26.9V (peak volts - diode drops), and passed through D2 (now down to 26.2V) into a Zener diode D3, which is a 9.1V diode!  D3 has to pull enough current for T1.1's winding resistance to drop 17 volts.  (some of this droop is provided by R118 and L8 as well.) 

Toasty!