Ok, I fixed it.
It was the white tape sensor in the lid after all.
Although I already overruled that sensor by putting tape over it, I noticed that fiddling with the sensortip (under the tape) by pressing it even harder or tapping on that tape, it triggered the error of stopping or shutting down the player. This was all possible because the lid was fully open while the tape was playing.
How did I fix it?
I first dismantling the lid completely, until I had the circuit board with the panelswitches and the LCD screen laying loose. Then I soldered a wire between the 2 pins of the sensor on the circuit board, effectively overruling the sensor. It is the same as what the tape did but then permanently and without the interference that the moving tip caused.
I tested and the problem was completely gone. Could not reproduce it.
Then I decided that that was not an elegant solution, because now the player is tricked into thinking that there is always a tape inserted and that could potentially give problems like opening the lid while playing and tape jam etc. Did not want that. You don’t want to go that route. It is there for a (security) reason.
So I tried a different approach: to clean the sensor (which is basically just a switch). It clearly was a faulty switch that gave wrong signals when it was pressed or released and anything in between. It resembles the problem of crackly pots or faders in analog equipment. It just gives strange effects in electric circuits.
The solution for that is 60-WL-61. What does that mean:
- clean it with Kontakt 60 (contactspray). This is aggressive stuff, so you do not want to leave it there. It solves corrosion and restores metal contact.
- rinse it with Kontakt WL. Flush it well with this and let it dry.
- use Kontakt 61. This will give it a protective layer to prevent future corrosion and wear.
This is all best done while the board is still dismantled, to give proper access to the switch which is basically open at the back.
After treating the lid sensor like this, the problem was gone and could not be reproduced. So now I have a happy player that can go back to its rightful owner again!
For a little more information about the cleaning process see here: https://www.reeltoreel.nl/wiki/index.php/Cleaning_contacts_-_contact_spray