Bizarre CD-Rom trouble - update

[pardsbane at offthehill.org (Josh Pollak)]

On Nov 23, 2004, at 2:19 PM, Josh Pollak wrote:
> Did without screws, did outside the box, the drive was slave, but I 
> switched it to master, tried the other ide connector.
>
> I'm down to:
>
> Try another machine
> Try another ide cable (the one I'm using is the 'split' one that came 
> with the Shuttle case)

Ok, so tonight I tried one of my fried drives in another computer. I 
didn't connect the IDE, just the power cable. The drive wouldn't eject, 
so I decided since it clearly was now 'disabled', I might as well 
disassemble it and figure out what is going wrong.

I don't know how many of you have seen inside a CD Drive, but basically 
there is they tray the disc sits on, and below that a hinged platform 
which carries the laser and the disc-spinning mechanism. The platform 
raises up to sandwich the disc between the motor and a freely rotating 
'cup' on the fix on top of the drive. When you press the eject button, 
a complicated gear system lowers the platform, and then ejects the 
tray.

Well, thats what's supposed to happen anyway. So with my drive 
disassembled, I press the eject button. The platform twitches, but 
doesn't drop down, which means the tray can't move (they are on the 
same gear system, so the tray is fixed until the platform lowers), and 
that's basically why the eject is broken. But I can't figure out what's 
holding the platform up and not letting it drop.

I found that by actuating the emergency eject lever, the platform could 
be forced to drop, so there isn't anything physically binding it in 
place (I think). I took the upper rotating cup (that holds the top of 
the CD and becomes the top of the 'CD sandwich') off the drive and 
discovered that it was magnetized. I think its supposed to be, though 
I'm not positive. Anyway, with that removed, the platform lowered and 
tray ejected without a problem. Apparently the motor that drops the 
platform either is no longer powerful enough to overcome the magnetic 
force pulling the platform up, or there something (an electromagnet?) 
that is supposed to counteract the magnet but isn't being engaged. Or 
the upper part isn't supposed to be magnetized in the first place, but 
I doubt thats the case.

So now I know what the problem is, but I'm not sure how to figure out 
what's causing the problem. It could be a fried circuit, it could be 
some logic in the drive telling it to remain locked, I have no idea.

I'm just going to resort to an external drive I guess, the PC works 
great otherwise. If I can find another drive I'm willing to sacrifice, 
I might try swapping the IDE cable and see if that keeps the drive from 
dying.

-Josh