The problem could be a number of things. Perform a continuity check
on your coax cable and the 4-conductor control cable. When you press
the tune button a brief start signal is sent to the tuner via the
white wire of the 4-conductor cable. The tuner then puts the radio
into transmit, via the green wire, with a 10 watt cw signal. You
should see the TX icon on the 802 display. If the tuner detects the 10
watt signal, it will initiate a tune cycle. The TUNE icon will flash
and you should hear a buzzing sound from the tuner. If the display
immediately shows the THRU icon after pressing TUNE, the tuner is not
working. There is really no reason to "open" your radio to transmit on
any frequency unless you want to operate on the ham bands. However if
you insist, the procedure given was wrong. You must press and hold the
2, MODE, and TX buttons and then turn the radio on. If you do decide
to open the tuner, be advised that there are nuts and lockwashers
behind each of the 10 screws holding the cover on. Even if there is no
antenna or ground whatsoever, the tuner will still try to tune and you
should hear the buzzing sound of the relays.

Eric