Hello! One month ago I bought from somebody this radio cassette https://www.radiomuseum.org/r/craftsman_record_0_matic.html . Theoretically works pretty good on AM, Tape and a little bit on FM. The AFC also works. Here is the diagram from the interior ticket: The radio cassette has a hybrid design with both Si and Ge transistors. The minor problem is a screw that is locked and when I tried to rotate broke down. The big problem is that even if is on tape or radio, the device makes from time to time an unusual noise; even if it is on low or higher volume. I tried to change most of the capacitors but in vain. Even the power socket I change, also in vain. I tried to power it from 9V battery but the same noise appear. I cleaned the rec-playback switch and the potentiometers but in vain. https://vocaroo.com/i/s0K8qYqNnINd Note: -at the end of volume potentiometer if I collect the signal to an external amplifier there is no such noise; -also at the colector of TR104 if I collect the signal to an external amplifier there is no such noise. What should I do?