Ideas for troubleshooting a noise generator on a PCB
Re schematic, sometimes it takes time for the images to show up I guess, and I didn't see a reference to it in the text. 

Have you measured the AC voltages to see if the transistor is producing any noise? Multimeter on AC range, most are AC coupled so on a 200mV range you can see 100uV noise for 3.5 digits and 10uV for 4.5 digits basic multimeter. 

You are using an ugly bias scheme for T3 (why not Q3?)- it's beta dependent. 

If you can't improve it, then adjust R21 so the voltage at the collector of T3 is where it should be (looks like about +1V would put it in the middle of the available swing).