"Art Deco" wrote in message
...

Anyone know how this works? Is there a sensor that recognizes the
transparent bits at the beginning and the end of a VCR tape?

I have two Sony VCRs that upon rewinding come to a crashing halt
rather than a smooth stop.

Thanks for any advice/suggestions.


If you look at the bottom of a VHS cassette, there's a hole near the flap
halfway between the spools. The hole is for the "light tower" which is a
plastic pillar with a LED (or bulb in older models) at the top. If you press
the latch at the side of the cassette so you can lift the flap, this will
expose a tiny slot at each end, there is usually a photo-diode at each side
of the deck lift in the VCR.

In older VCRs bulb failure was fairly common which was usually sensed by the
microcontroller and caused the VCR to refuse to operate rather than work but
fail to slow at the end of the tape. Most modern VCRs use the sensors under
the spool drives to calculate the ratio of tape on the two spools and cut to
a slower speed as it nears the end of the tape. If your lucky its these
sensors causing the problem and they're opto-reflective types with just some
dust to clean off - if they're Hall effect sensors you probably have a MPU
fault!