I have here today one of Denon's first three head flagship cassette decks. Mine is a Japanese market DR-F3, but it was available worldwide as the DR-330. This model uses a somewhat rare quartz locked belt drive setup.
What we have here is a rubber nightmare. Not only has the old capstan belt expired and gone hygroscopic, resulting in flywheel damage, but this transport also uses three unobtainium idler tires to drive the reels. Did I mention the coreless reel drive motor? It has one of those as well, and good luck finding a replacement if you need one. I'll try my best. Maybe that's good enough?
Capstan belt: 74mm dia. (232mm IC) x 4mm
Counter belt: 226mm IC x 0.7mm
Reel table tires: 13x20x3mm (Fix Your Audio/Van Hurban). Not ideal. Needs to be 17x22x3mm. Factory tire is T-shaped but does not need to be T-shaped to work.
Idler tire (improper): AS-568 SB-111 o-ring. Fix Your Audio's 14x19x2 or 14x20x2mm idler would likely work better.
Music: fritefromagesauce.bandcamp.com
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My Favorite 5 Cassette Decks for Sound Quality:
1 - JVC TD-V931
2 - A&D GX-Z9100
3 - Aiwa XK-007 / Carver TD-1700m (tie)
4 - Sony TC-K666ES
5 - Denon DR-M3 w/ UKZ Caps
0:00:00 - Intro
0:04:27 - Pre-service check
0:09:38 - Cleaning the case
0:11:52 - Transport removal
0:18:28 - Begin transport service
0:25:35 - Accessing the flywheel and reel drive parts
0:35:53 - Servicing the reel drive
0:53:19 - Greasing the linkages
1:00:09 - Capstan motor service
1:11:11 - Flywheel damage
1:12:39 - Front of transport service
1:29:40 - Head condition shots, post service check
1:35:22 - Wow and flutter check
1:39:14 - Play testing