[jasejames]

Thankyou very much for the detailed post, this is all very helpful and I will of course update.

I have ordered a new idler (which I won't use until it's clear the current one isn't doing its job any more), along with R49 and D6. I will perform the torque upgrade first then work through the other suggestions.

I think this particular unit is unmolested and in good condition. There was "honest dust" on the boards etc when I took the top off and no fingermarks etc, and the belt that snapped looked like it may have been the original. I've not experienced any issues with the tape being slightly loose on eject or anything like that, so I think this is a good candidate to work with (carefully as I don't want to make things worse myself).

I'd rather not have to pull the reel motor apart if I don't have to; I've pulled cassette motors apart in the past and it's never ended well lol. Thankfully they are usually ten-a-penny. Are you suggesting that replacement brushes are available for these motors?

BTW one thing I've not yet been able to work out is how to take out the cassette loader to get to the reels underneath. That wasn't a problem when replacing the belt as it was possible to fettle the belt around the idler, but if I'm going to start taking the idler assembly out this method won't work. Is there a tutorial somewhere on how to sort this? As I say I am loathe to start experimenting with an essentially-working unit that seems in good order generally.