I rolled up the screws with cotton thread and now my meter shows nothing between the screw and middle leg of TIP-50 transistor. The voltages seem OK too, all LEDs are glowing (but the LEDs on small PC boards are glowing less than the others).
Now I have the noise in left channel. The noise changes in time... When I turn the amp on I hear loud noise in left channel, after about 10-15 seconds it sounds way more quiet (some people don't notice it at all at this stage) and then it produces BOOMs occasionally. The noise is not related to the volume level. Once again the only potential problem I see is that 2N2222A transistor which was soldered without leaving the space between transistor body and PC board. I tried another 12AU7 but the noise is still present. Could you help me, please?