There is more to know about the GX280DSS than a manual can tell you. While it is one of the finest decks made for quad, it does have a flaw. The control board is a double sided board made in the early days of double sided boards, and they had a few things to learn. The main thing is that if you connect one side of the board to the other using rivets, it doesn't work. The rivets expand at a greater rate than the board and the copper land will break away from the brass rivets. It's a hair line crack, but it can cause some bad effects. These are:
Perpetual autoreverse: the machine continuosly autoreverses.
Sudden rewind: The machine will be playing along and all of a sudden it will go into rewind mode.
Sudden stops: The machine will stop without being commanded to do so.
There is a permanent fix and it is worth doing, because the end result is a very good quad machine with heads that don't wear out. The rivets must be desoldered, and a piece of wire is soldered to the land on one side and passed through the rivet and soldered to the land on the other side. Telephone wire is good for this. Once you do this, you will have a very reliable quad reel to reel. oh, and you might have to replace the chips because they tend to get noisy. but that's another story. No more surprises after that. Happy hunting!
The Quadfather