Hoping for operator error:
It's too easy to be in a hurry and to connect an input to the bottom row (Preamp OUTs) for Channels 1, 2, 3. You won't get any sound. Channel 4/5 is somewhat fool-proof though. There's no Preamp Out for that channel.
Another thing to check is the the Channel Trim Controls.
If the Trim controls for channels 3, or 4/5 were all the way off, you wouldn't get any sound.
It the Trims for 1, 2, 3 were all the same, then moving an input from channel 2 to channel 3 - you should have seen activity on the trim light on channel 3. When you tried 3 and 4/5 did you see any activity on the trim lights?
If you're checking things today - select the Comp/Gate on the Rotary Selector and make sure that KickGate and Noise Gate are both bypassed.
Still hoping for operator error - did you have the Mute buttons lit for channels 3 or 4/5?
Oh - never mind - you said you checked these.
I think that's it for possible operator errors.
Any luck at your end?
If not, then it sounds like the T1 will have to be serviced. Here's how to reach Bose Support.
Unit 3/2 Holker Street
Newington NSW Australia
Bose Pty Limited
Tel: 61 2 8737 9999
Fax: 61 2 8737 9922