BEO CARE provided the instructions:
Applies
to BeoSystem 3 with built-in ATSC tuner only.
Factory
default instructs DTV BUTTON on Beo4/5 to select the
ATSC tuner connection from an outdoor antenna or a direct cable
connection via F Connector # __? on BeoSystem 3.
If
neither an outdoor antenna or a direct cable connection is to be used
you can set up BeoSystem 3 so the DTV button will access one of the
AV Inputs.
Touch
MENU (if this takes you to “TV Setup Menu” skip the next
step)
Touch
MENU > takes you to “TV Setup Menu”
Scroll
to “Options”
Touch
the RED (not the red dot/STANDBY button) ARROW BUTTON,
then immediately touch GO > takes you to “Customer
Service Menu”
Scroll
to “Adjustments” and touch GO
Scroll
to “DVF”
Touch
> BUTTON to select “Off”
Touch
GO
Disconnect
BeoSystem 3 from power and leave it disconnected for at least 30
seconds, then reconnect it to power. Putting BeoSystem 3 in Standby
is not sufficient. It must be disconnected from power.
You can
now go into the “Connections” menu and you will see “DTV” is
available as an source button for the AV inputs.
Hope it helps somebody in the future!