That's great to hear mate, congrats. Must have been a bit of a mission but I know how determined you are. Did you track down the clunk clunk noise? Was it a gear or just an idler "chattering"? Also with the belts did you re-surface them/take them off to do this?
On the other hand my 480 has stopped recording. I was playing back something recorded in it and the sound got really trebbly and tinny like it was over biasing, then gradually I started hearing the previous recording on the tape fading in like it was not erasing properly, with a crackle and pop of what I was recording stuttering along in the background. There is nothing wrong with the transport and the heads are perfectly clean so its not mechanical. The record switch on the circuit board has been de-oxed and worked back and forth 100 times. I think this problem is electronic related, can't be bothered fixing it as have too much to do this weekend recording wise, so will record with the trusty JVC TD-V661. First time a Nak has given me trouble like this