i've got a tr-606 and it works fine. the only problem is that it runs only with batteries. so i tried to resolder the power supply contacts on the board - nothing. does anybody knows this problem or how to fix it?
Could be a crack in the board, 303's and 606's are bastards for that. Use a multimeter with a continuity tester to make sure the tracks are actually connected for the power jack for as far as you can manage. Other than that you could check the power jack is actually working by testing the voltage on the board side.
Next step would be to check out the voltage regulators if there are any or possibly a diode near the power input might have blown.