I just got a used Adcom GFA 555, it looks different to all the 555's I've seen, so I think it's kind of old.
The amp was cheap because the right channel RCA Jack is broken. I thought it was going to be an easy and cheap fix, but the two (2) RCA inputs are in one plastic unit. I need help finding a new RCA jack "thingy". At least the amp powers up and seems to work.
Below are pictures of the amp opened up and the RCA jack plastic unit/thingy
It looks clean, the caps are not swollen or leaking everything looks great.
The broken Right Channel RCA Jack
The back of the RCA jacks
The plastic RCA jack unit
This is where the RCA's are soldered to the board