ZX Spectrum Easter Egg - Spectrum +3 Diagnostics & Sound to Light

Reset your speccy and as soon as the screen goes blank, hold Q,A,Z,P,L & M together.

I can't remember if this enters the sound to light or the diag. screen.
If you get a black screen, try playing a tape (connected to the audio input) and you should get a colourful display that reacts to the volume/frequency of the tape.

In addition to this, hold the following keys together : U,I & O.

The computer should then enter a diagnostic screen used for Quality control on the factory production line.

From here you can test the ULA, keyboard, disk driver, tape input, etc. WARNING ! The 3" disk inserted will be WIPED so please don't have a games disk inserted !

This is from memory and the keys may be incorrect - try variations and you'll get it in the end !