1996 850 Heater Control Light Bulbs (ECU)

Hello all

I have a 1996 850 in need of light bulb replacement for the passenger
side temperature control dial. I bought three bulbs from my Volvo
dealer and a Haynes manual that says to remove the radio and then reach
inside the radio cavity and depress the locking button on the underside
of the heat control unit. There is no button on the underside of my
unit but there appears to be a place where a button was previously
located and may have fallen off. Can anyone tell me any other ways of
dislodging this unit?

Thanks