Citation 7.1 amp bridging problems

I just got a pair of Citation 7.1 power amps and set them up on my test bench. They did not come with manuals. I first worked through each amp, channel by channel, just testing to see all the channels worked OK. They all worked and sounded fine, though I wondered if I had enough power with them to drive the ACI jaguar 2000's I was testing them with. I'd just been testing out a big Krell KSA 200 last night so that was fresh in my mnd... Anyway, so then I went to test the bridged channels on the first Citation 7.1, and I hooked them up exactly as diagrammed and described on the back of the amps, turned it on, and got no sound, then a loud click like a breaker tripping and a red light on the front panel. Took everything off checked for shorts, etc., hooked it up again, same thing. So I tried the other amp. Same thing.

So I decided maybe it was something about the impedance of the speakers or the cables the amp wasn't liking, and I had a pair of Avalon Avatars nearby so I hooked them up using different cables, again to each amp, with the exact same results.

Can anybody suggest to me what to try next? I may be missing something really silly--I don' have a manual and can't find one on the web. But as I say I am pretty sure I wired it exactly as diagrammed on the back panel and checked and rechecked (and had a friend with me helping). I wired just using the red terminals on both sides when switched in to bridged mode, and with the polarity as shown on the amp. Nothing. Any help would be appreciated!