Don't see a fan on the 7704a. Searching in the manual can't find any reference or illustration showing a fan. And the temperature is even behind each of the pass transistors so it does not appear any one element is generating a bunch more heat than the others.
Maybe this is normal? But as Maui said 'Hot hot hot'. (You have to be conversant with Disney princesses to understand. My assistant is 4 1/2.)
--
W0MPM John
John W0MPM