You just need to be able to get the speakers to react to the remote control in order to display the current firmware.
If you don't need to know the current firmware, then you can skip that stage.

The firmware file for the 7-segment displays will normally end in _7.

Speak to an HH-friendly dealer in order to get the correct firmware.

If you load the wrong version, then the displays will do strange things...

Cheers,

Steve

Main: 861v6 (LPS), 808v6, UHD722, DSP8000SE Anniversaries, DSP5200.2HC, DSP7200.2, SW1600, Sky Q, Cambridge Audio BD, Roon, M80
Office: 861v4 (LPS), 818v3, 800v4, HD621, M&K S150P, DSP5500HC, M&K MPS2810 sub x2
Son's system: 861v4, HD621, DSP6000.2, DSP5200HC, DSP33
Spare: MCD, 100 Series, 200 Series, 500 Series, F80s, C15s.