The Sony Walkman WM-EX662 and WM-EX550 are almost identical high end portable cassette players. I have had mine apart. I took some pictures which you may find useful.
The only difference is that the the 550 uses a standard AA battery and the 662 has a rechargeable gum-stick type battery. This is why you see in some of the photographs I have “hot wired” an external battery to the 662 to get it to work on the bench.
A common problem with these otherwise excellent players is the drive belt, which stretches over time and needs replacing. Be sure to get the right type if you are doing this. Generic belts will not do because the unit has a clever trick to save battery power. The small black pulley moves to change the tension on the belt. High tension is only used for fast wind and starting up. When playing the belt is slacker, placing less load on the motor. For this to work the properties of the belt are critical. This is how they achieve nearly 30 hours of playback from a single AA.
The following photographs have been provided for reference. Clicking on the pictures will open the full size high resolution original photographs. This is great for reference, but heavy on bandwidth. You have been warned.
