Technics cassette deck records automatically when pressed play

Hi

1. Without going into too much of the detail, there are two holes on the top of cassette. Cut 2 cubes from any piece of rubber -- pencil eraser will work and stick in these holes to prevent recording switch to engage. This way you will most-likely succeed playing any tape without hassling.

2. Levers in this mechanism do get stuck and may need gunk removal. Refer to products Deoxit D5 or F5. The budget solution will be CRC products you can purchase from Home Depot or any major hardware store.
You will need to open your deck and visualize the levers feeding tape and engaging switches...

Good luck.
  

Czarivey has good advice, but he has #1 backwards:

Opposite the working edge is the "tab edge" or the edge that has two small "knockout" tabs set into place. When the tabs are in place, they depress a small pin-like mechanism in the left rear of the cassette well.

When the tab on the case is intact, this pin-like mechanism (the anti-record device) releases the record button and makes it possible to record on or over material that is already on the tape.

When the tab is removed or knocked out, the pin slips into this opening, leaving the record button locked and unusable so that it is not possible to record on or over material that is already on the tape. This feature protects valuable recorded materials.

To reuse or record over a tape with tabs that have been removed or knocked out, cover the opening with a small piece of cellophane tape.

If you are never going to record over the tapes you are using, just knock out the tabs.  That should prevent the record function from working.  However, you might have a faulty logic IC control chip that is causing the problem.

Is the timer switch set to "rec"? If so, it should be switched to off.

Thank you, both, for responding so quickly. I was aware of the function of the tabs on top of the cassette and in the past I have put out lots of them in case I would accidentally press record.
I am interested in the defect causing the deck to record on my cassette. You have given me two possible options. Thanks for those.
For the chip I have to go to an expert. But I can try and follow the solution Czarivey gave me. Should I be able to find that lever easily?

Even with the timer switch set to Off, the recording starts. It would be great if that had solved the problem...

Czarivey, I found the lever which engages the recording.
Still, it makes no sense that the lever causes the problem.
It doesn't send the signal to begin recording. It just makes recording possible.
So, the suggestion that a chip may have a defect, sounds plausible to me.