I just bought this machine. It's in great shape for being forty years old and seemed to work fine until the machine started to slow down while in play. When I engage 7 1/2 IPS I can hear a fan that starts to run. It's only when that fan seems to be running slow that the reel to reel will not play my tapes at the right speed. It only seems to do this at 7 1/2. I don't have any tapes recorded at 3 3/4 so I can't tell if it plays slow at that speed as well. Any ideas? This looks like a very complicated deck to take apart.