Heatmiser, you're the reason I'm about to tackle replacing mine with confidence. I joined a few forums in the past few days that I had been stalking, or shall I say internet research, and someone sent me a link to your dissemble of the 688 thread. So I say thank you! I have ordered 2 belts and just got a free copy of the service manual, so this weekend I will read over it. Next week I will replace the belt and the battery. Last week I took apart a 424 mkII that was given to me because it was dirty, had something lose in it and I was told that one of the channels or tracks (track 3?) wouldn't record. So what did I have to lose. Cleaned it up pretty good and got all 4 channels and tracks to record. I was getting this intermittent scratchiness going on (like a dirty pot?) when I decided to deal with that later and bring out the "big guns" (that's what I told my wife anyway about the 688). Before it started to randomly stop, I did manage to record a care-free version of Waylon Jennings "I Don't Think Hank Done It This Way," which I was really pleased with considering the effort. Any way, I will keep you posted on my progress.