heat in sa-ht75?

I had the same thing happen, unit got warm, but fan didnt come on, heard a big bang in my speakers, and then the unit shut of itself.
I let it sit a few minutes, turned it on again, and same thing, big bang, and it shut of.
I also took the fan of, it works, then I looked at the screws holding the amp to the heatsink, and tightened them, they were not tight!!
Now I can play it for hours, ran about 16dB, but no fan comes on, now after reading about 8dB, I tried it, but no fan action.
Will try to find 12v on board, to make the fan run constantly.....

Hope this gave a little more info about the unit