FYI - the default password is 'dbc' but your logon string is missing the password - hence the failure (probably an 8017 error).
The following logon string should work:
dbc/dbc,dbc
The three dbc's are:
dbc#1 = tdpid - i.e. which Teradata system you want to logon to
dbc#2 = username
dbc#3 = password.
Dave