Reply to warning
Hi I always put either a very big wattage 20ohm resistor in the power supply lead or a car lamp bulb a rear tail light is good. This will protect the circuit against shorts, allow you to find "hot" items but still allow (moderate) power.
I used to teach and the above is always good, gosh its prevented many an expensive day.
The first thing to check is your wiring, out of all faults presented to me wiring came first followed by defective soldering. In fact a guy who had passed out of Moscow University, and a US one as well, had got to be a proffessor came to me at the company I worked for to try to solve a problem with an amp he designed and built.
The problem was a dry joint. Me I have basically no qualifications, heck they were trying to teach me U, grm etc of valves, I was designing and buiding using 109's, 106's and the like.