I was looking after a service manual. I thought it would be a long shot but I thought I'd try. I was hoping to find a service manual to guide me as I attempted to fix a couple other problems. My 'Backspace' and 'Repeat' do not work now. I took the cover off to put a spring back in place that was causing the shift to be slow once released. I put the spring back in place, put the cover back and put the carriage back on. But once I put the carriage back on, something pops and disengages the repeat and backspace. And I can't figure out what.