Barney

Thank you for reply. LED doesn't light at this current but it is working with lower currents just fine. It is true that the lamp is using 5A but I still think there is some power left even if transformer is overloaded. I think this is the reason why LED doesn't light. However I changed the OPAMPs a few times (i have spare ones) but the problem is still there. Pins on transistors are connected the right direction. I'll keep searching for problem...

I have built a 5A version of this power supply. It seems it's working in some way but there is one 'load' problem. When I connect the 12V/60W lamp to PS and set both potentiometers to max. values I get around 11V at the output. This is somewhat strange so I think in theory this PS should burn out that kind of lamp. The problem is why is the voltage drop that big. There is also another strange thing. I was measuring voltage levels in the circuit. Most values seem ok, except some values around U2. When both potentiometers are set to min. there is few milivolts on the pin 2 and 3 but at the output pin (6) there is 10V. I don't know from where this voltage come from if the input pins are almost at zero value. In the other hand, when I set potentiometers to the max. the I measure around 3.5V at the pin 2 and 11.2V at the pin 3. At max. settings with no load connected I get 39V at pin 6. I am using 30V/7A toroidal transformer and 3x2N3055 as output transistors.