Transitors pass all the voltage from collector to the base and cause a short. Transistors are perfectly ok, they're not broken (I tested them). The voltage is rather high but they should handle it although they're (almost) working on their limits. (The amount voltage passed from collector to base seems to increase while the test circuits supply voltage is increased though.) There seems to be no faults in the circuit build. What could cause this? The circuit is a basic amplifier. Transistors collector connected directly to supply voltage (65 V), no resistor. Transistor used is BC546 complemented with BC 556 which has emitter connected to supply voltage. I'm amazed. What should I look for to get the circuit to operate? Everything tells me it's supposed to work. Supply voltages are OK without the transistors. With them the circuit shorts. I know this is rather tricky question without describing the circuit entirely but if someone has experience of problems or symptons like this, (in any circuit), I'd be thankful of some hints and suggestions of what type of fault to look for.