My Nakamichi Cassette Deck 1.5 has a distortion on the left channel. Bass is crackling. It occurs on both playback and record. Please find the service manual on attached. On the electrical adjustment section, I don’t understand it much. Please help me find the adjustment point.
Do you have an oscilloscope? Usually it may be caused by a bad cap (perhaps the unit must be recaped) or a bias has changed in some stages. Also suggest to clean the heads using a small piece of cotton and isoprophyl alcohol. Leave it to dry and test again. Keep us posted.