Like I said, temporarily put 1K in R13. That will allow the unit to power on without burning up. Then you can check thing with power on. The short (assuming it's a short) is going to cause a huge voltage drop across the 1K. Using ohms law you can plug in the voltage drop and 1K to get current. And more important you can see just how low the voltage is going. If it goes to 0V, then obviously something is very much shorting. If you get 5V then maybe it's more like an op amp output is pinned low. Narrow things down a little. Use your ohm meter to check resistance between -15 rail and 0V. If there are connectors that separate boards, maybe you can disconnect one to narrow things down further. There is no specific procedure for any of this. You just have to think about things logically and fiddle.
And you don't have to use the same transistor exact transistor in that power supply. There are lots of transistors that will work there (like BD140). But if you do replace one, you should probably replace the other with the complementary part (BD139 is complement to BD140). But that assumes that there's something wrong with that transistor which so far you have not said anything that makes me suspect the transistor specifically. In fact, if I had to guess, I would say it's actually no the short because it's not even connected to ground.
