I now have input boards for the very first GFA-555’s that came out in 1985. Judging from the serial numbers I’ve seen, there are perhaps less than 8000 of these amplifiers in existence. But they deserve to be restored!
At first glance, they look just like the boards in the more common 1986 version, but they are not physically compatible. The mounting brackets are spaced wider, the RCA input jacks are different, and the bridge switch is a bit chunkier.
If your back panel looks like this, then this is the board you need,
The other physical compatibility issue, is that once you remove the original plastic RCA jacks, you are left with a gaping oval hole in the chassis, to which you cannot mount nice gold-plated RCA jacks to. My solution for this is an adapter plate made of PCB material. It’s included with the boards, along with a pair of REAN RCA jacks.
More pictures of GFA-555 #5763. I’m keeping this one!