Sunday, October 24, 2010

Sony XC995 Repaired!

After tracing the spindle driver electronics, I determined that the controller was not even attempting to spin the DVD for some reason. That reason must exist somewhere earlier in the disk reading algorithm. Now I was starting to fear I would have to replace the whole DBU-3 optical assembly, available for about $99 on ebay.

I tried to re-calibrate the drive through the diagnostic tools built into the player (press Edit-Clear-Power in sequence while in standby). The calibration required loading a single layer DVD, audio CD, and a dual layer DVD. The calibration utility did not seem to help. No DVDs would even spin up. However, the audio CD I loaded for calibration started to play! So clearly, the hardware detecting the media type even before spinning it up. For some reason focus on DVDs was not possible. In retrospect this makes a lot of sense - it is probably much easier to focus on a non-moving target. Failure to find focus would result in the drive rejecting the disk.

Next time I loaded a DVD up, I pulled the disk a short distance away from the lens by sticking my finger inside the drive. I saw the lens focus and the spindle started up! Of course, it would not work with my finger sticking in there, but this was an excellent sign!

Now, in my initial attempt to debug this I had removed the spindle motor. This involved removing the plastic hub from the spindle shaft. Upon re-assembly I pressed the spindle hub on to approximately the same location as I found it. It turns out that the original hub installation had likely been pressed on a hair too much. Perhaps after a 1000 CD loads, and a bit of mechanical wear, DVDs started to be loaded just outside of the focus range of the optical system.

The repair was simply removing the spindle hub and re-installing with about 1/8" of clearance. Now everything is working!

Friday, October 22, 2010

Busted DVD player

Wow! Over 1.5 years since last post!

My Sony CX995V DVD jukebox stopped working last week after 4 years of relative reliability.

Some investigation indicated that the CD spindle was not rotating after loading each disk. My first thought was that the spindle motor must be bad. I spent time taking the whole thing apart and removed the spindle motor. I hooked it up to a 5v power supply and it spinned up like a champ. Drat. Now I had to figure out if the motor driver was working. I managed to locate some teeny tiny test points for the spindle drive voltages and solder some wire wrap wire onto them. Sure enough, no voltage across these points. Manually rotating the spindle motor did generate some measurable back EMF, so everything is hooked up properly, just no juice. Turns out this is driven by a Fairchild Semi servo IC designed specifically for CD drives. It has 5 output channels to handle all the various motors in a modern CD player: sled, spindle, focus, etc... Now it seems that all the other functions of the drive are working. I can see the sled move back and forth, the optical assembly was definitely trying to focus. So the IC seems to be mostly functional. Next step: test the inputs to the motor driver to verify that the controller is indeed trying to spin the CD when it is supposed to. My prediction: it is NOT going to be sending a signal to the motor driver IC. If it is just the motor controller chip, there is a SLIGHT chance I could locate a replacement chip and repair the main board. If I have to trace this thing back much further, I will probably run out of leads as to what needs fixing.