Marconi 2024 - Unlock

[Andy Watson]

I have acquired a Marconi (IFR/Aeroflex) 2024 signal generator. All appears to be in order except the AM modulation depth - it appears to reach full modulation at approximately 92%. Does anybody know how to unlock the "Level 2"  calibration functions without the 6 digit key? (Level 1 unlocks with the default 1234, but the level 2 code has been changed.)

Thanks.