Mcintosh 2205 amp limit tripped at 90 db

wondering if anyone can help. I have a mc 2205 running my B&W 804's but it doesn't seem to be putting out the power I was expecting. The red trip lights kick in at about 90 dbs and the meters read about 100-150watts, which seems pretty low for 200wts per channel. I have them hooked up to the 8 ohm outputs. I also have it plugged into the preamp (mx 130). INn addition the display lights seem to be dimming when it is cutting out.

My brother thinks it is because it is plugged into the preamp and not getting enough current, but before I pull it apart I want to hear what you guys think.

I like the 2205 but it is 30 yrs old and may need to see a tech, but first try these 2 things.

Plug it into a wall socket, even if you have to use an extension cord. (Get a heavy duty one if you do.) I DO NOT like the idea of plugging it into the back of the 130. Even if you weren't having this problem, the turn on surge will eventually take out the wiring.

Second, switch to the 4 ohm tap. Even though B&W says 8 ohms, there are dips and phase angles that might make your amp happier on the 4 ohm tap. Good luck.
Good suggestions from onemug. Its not realistic to think that the "aux power outlet" on the pre can supply enough current, IMO.