Unless the firewall hardware is quite old, or the unit has developed a fault, establishing a serial console connection should be pretty easy.
The terminal application (and I happen to use an open-source product called PuTTY) needs to be configured with the following settings:-
- Speed - 9600
- Data Bits - 8
- Stop Bits - 1
- Parity - None
- Flow Control - None/Off
Older appliances were supplied with a serial cable, but because there wasn't necessarily a use for it, the console redirection setting in the BIOS was disabled. The behaviour of the console redirection also changed slightly between v6 and v7 which meant that on some models it was necessary to change this setting before a serial connection would work properly. See KB61286 for more information
Note that when using a serial connection not all terminal programs support the use of the Function keys, so you will still need to connect a physical keyboard to the appliance should it be necessary to press F1, F2 or similar - KB64036.
If you are unable to see anything on a screen connected directly to the appliance this would suggest that there may be a more serious problem. In which case you should contact McAfee support. The appliances are supplied with a hardware diagnostics CD (or USB memory stick) which they may ask you to run, but if you can't see anything on the screen this may be irrelevant. In which case if the unit is in support and still has hardware warranty, they may need to sort out a replacement.