I know that this is an old post...
The repairs from 2011 were only partial. It was mainly old and worn out controls for the equalizer, volume controls and the rest. I did not possess the original manual at the time and because of that, I couldn't have possibly known that there were some other functions on my boombox that were not functioning.
The complete list of recent repairs I will put here:
Controls of the equalizer and other controls were not functioning correctly.
Tape1 sounds bad because the tape head had been replaced with the wrong tape head and the HK-9000Z had been adjusted for that tape head.
Loose connections on the back of the HK-9000Z for the Phono, CD/AUX and AC INPUT.
Buttons for the LCD Clock function badly.
Plastic pieces for holding the speaker wire along the bottom rear of the HK-9000Z are in very bad condition.
Rear board has been cut to make new connectors for Phono and CD/AUX.
LCD Clock battery holder had been replaced with the wrong LCD Clock battery holder.
Tape1 and Tape2 cassette doors have cosmetic damage to the paint surface.
All buttons needed to be checked for proper operation, one of them had not functioned for a while.
The technician then found that the tuner, while changing stations had not been smooth. That problem was fixed.
First return: The right channel had distortion given certain settings on the equalizer. That problem was fixed.
Second return: The auto stop function on Tape1 was not functioning.
I have tested pretty much the rest of the functions and they are all working. I now have an electrically fully functional HK-9000Z! I am very happy.