Shorting out the cassette lamp was a common trick. The bulb helps the machine detect the end of a tape. When the bulb burned out, the tape functions like rewind and play all stop working. This is to prevent damage to the tape and video heads. Twisting the bulb's wires together enabled the machine to start working again temporarily, so you could see if there were any other faults and determine whether or not it's worth repairing before spending money on replacement parts.
In my experience, temporarily shorting out the cassette lamp didn't damage the electronics. You can try it to test the machine, being careful not to let a tape reach the end.
Replacement cassette lamps were available complete with the blue wires and 2-pin plug. Examples here:
https://www.donberg.co.uk/catalogue/...res/17053.html
https://www.donberg.co.uk/catalogue/...res/17050.html