Viglen - Backdoor Combination?

[bandgeekmafia78]

Hi,

 

We've got some really REALLY old Viglen thin-client terminals that have gone haywire. Basically, I need to access the 'backdoor' to make a few changes. No idea what model no but then are thin and blue!

 

Anybody know what the combination is? Someone told me its something to do with holding down TAB (?) on startup.

 

If anyone can shed any light on my problem it would be much appreciated!