More fun with Pioneer CDX-FM1235S Car CD changer

[Brent P]

I've played with it some more, after checking the motor out of the unit
I put it back in and soldered extra leads to the motor pads to get a
more accurate picture of the voltage going to the motor. The error 12
it gives according to the manual is that the unit cannot focus.

The sled moves back and forth, the laser area moves around alot trying
to focus durring the start up. My guess is that it is good. So I
investigated motor speed. The motor seems fine on the power supply
level, smooth and fast operation.

In the unit durring start up the CDs spin up, spin down and then stop
try again repeat, eventually it gives up.

At start up the voltage is a nice 5.85V, it then drops off to about 2.1V
for a moment and then the speed drops, the motor settles in at about 1.55V
for a while, speed is held, then it drops off to zero as the motor stops,
spikes at about -2.8V as the motor stops. Then it immediately restarts the
cycle. The CD spins down alot faster than it would naturally so my
assumption is that the motor controler is sending it the negative voltage
to purposely stop the motor from turning. Is this a correct assumption?

My best guess is that this data shows the motor control is working just
fine, doing it's best. I don't know what to try next. Maybe give the sled
a real close going over under a magnifing glass.