hifi engine

Sony TC-490 Dual Cassette digital counter inoperable

I just replaced the belts on my Sony TC-W490 dual cassette deck (that I haven't used in about 6 years). All went well mechanically (I think), Deck "A" now works fine but Deck "B" starts and stops.

The digital counter is not operating on that deck in any mode. For the brief time the tape spins the sound is good and FF/Rew both work before it quits. I'm guessing the unit thinks the tape has stopped since the counter stays frozen on zero.

Anyone know where this unit senses tape movement and relays it to the counter? I don't see a mechanical connection or a belt. The counter is digital and I remember it being consistent with the time the tape had actually played.