hifi engine

AKAI 4000DB Reel to Reel - Loses one channel after running a bit..

Hello all. I have an AKAI 40000DB reel to reel unit that has been sitting on my closet shelf for some time now. Wanted to copy some old tapes of records to mp3 via my computer. The AKAI runs fine for appx 15 minutes +/- then the right channel just "drops out" so stereo becomes mono. Tried another tape and it does it too. Downloaded the service manual (THANK YOU HIFIengine) but its obvious I don't have the test tapes, oscilloscope, and other test tools. IS this something simple (or a common problem) that I can fix or am I screwed and will now have to find someone that can fix it and reasonably $$?? Thanks and I await any responses..