Larry, You sure know your Fishers! All the info from one poor quality photo.
Here's the Chassis Layout Diagram that you asked for:
View attachment 681175 As you can see, Fisher refers to it as an E-492B. Looks like they may have added an "AT" suffix to the model number. It's all very interesting.
The guy that I got it from said it never worked. I'm not sure how long he owned it but he only used it as a stand for the TV.
I got it home, replaced the blown fuse and she came to life! )I did have it on a DBT). The next day, I thought I try the Dual - shore 'nough. it works, too!
One channel keeps dropping out, so I shut it down after a short time.
All-in-all, I think I got a pretty sweet deal!
Thanks, again for the history info and the word of warning.