Replacing a DC's spindle motor

sorewinner · Post by **sorewinner** » Wed Nov 27, 2002 2:17 pm

Since that [spindle motor] is the part in my DC that died, and since it seems to be the only part not sold (

), I was thinking:
Since the DC's laser assembly is a 12 speed, could I simply replace the motor with a comparable one from a 12x CD-ROM drive? I don't see why not, but I'd like some informed opinions. Thanks in advance.

mariobro · Post by **mariobro** » Wed Nov 27, 2002 5:47 pm

A friend's DC once had this problem, and we were able to get it repaired by a very crafty electronics tech. He had never worked on a DC before, but he was able to diagnose the problem and fix it, without replacing the motor. He had a lot of experience with portable CD players though.

So you could look for someone with mad electronics skillz, and see if the motor can be repaired, or replaced. My fiend's DC is still going strong, it started to reset itself, but it was the common PSU pins problem, and we fixed that.

Hope this helps.

sorewinner · Post by **sorewinner** » Thu Nov 28, 2002 11:22 am

I appreciate the input, but I wouldn't be asking the question if I was willing to pay a tech $45 an hour.

Does no one know the specs of the DC's spindle motor?

Are there any message boards which discuss this kind of thing? I tried Gameconsolerepair's forums, but never got a response.

farrell2k · Post by **farrell2k** » Thu Nov 28, 2002 6:28 pm

Just replace the motor with another 12x motor. They're all ther same and you'll have no problems.

mariobro · Post by **mariobro** » Thu Nov 28, 2002 8:49 pm

We're in a sort of Catch-22 situation here...

If someone has detailed specs for the DC's spindle motor, and knows a suitable substitute, and how to perform the repair, I suspect he wouldn't give the info away just like that, or do the repair for free. I once posted a link to a .PDF that's a teardown report for the DC, with pictures and a lot of part numbers and specs. It might just have info on the spindle motor:

http://www.portelligent.com/samples.asp

It's a big download, but trust me, it's very useful. I really advise you to get it.

Hope this helps.

sorewinner · Post by **sorewinner** » Tue Dec 03, 2002 7:43 pm

Mariobro, that link LOOKS like it would be useful, except I will never pay for online content.

Farrell2k, I like your thinking

. I didn't think it would be a problem, except I seem to remember reading somewhere that it's the Dreamcast's firmware, and not the laser, that allows it to read GD-ROM discs. Damn, I wish I could find that link...

I don't know. I figured a board dedicated to modifying hardware would at least have a couple of people with knowledge of the inside of the machine its (the board) readers were modifying.

MidnightObsidian · Post by **MidnightObsidian** » Wed Dec 04, 2002 12:00 am

sorewinner wrote:Mariobro, that link LOOKS like it would be useful, except I will never pay for online content.

Farrell2k, I like your thinking . I didn't think it would be a problem, except I seem to remember reading somewhere that it's the Dreamcast's firmware, and not the laser, that allows it to read GD-ROM discs. Damn, I wish I could find that link...

I don't know. I figured a board dedicated to modifying hardware would at least have a couple of people with knowledge of the inside of the machine its (the board) readers were modifying.

Replacing the rotary motor on a Dreamcast is extremely simple. All you need to do is find a rotary motor that will both fit into the place where the DC's motor goes and also either fit the existing nub or has a nub that will substitute and fit into the existing plastic well. Virtually any motor will work, be it from a portable CD player, from a PC CD-ROM drive, or from whatever else. If it fits and it spins, it'll most likely do. In the worst case scenario, you'll have to unscrew, remove, and resplice another motor on.

Just splice together some wire to both extend the length of the wire and to attach the original plug (which will in turn attach to the GD controller board). To mount the motor, you'll have to spin the nub so that the holes in it will show two TINY screws, which you'll remove. Put the new motor in its place, realign the screw holes, screw the thing in, and attach it to your GD controller board, and you're finished.

It's a rather simple repair, but the splicing can be a little difficult, especially for people without much experience in electronics. If you need any more help, feel free to ask.

By the way, I was actually the one that discovered that it was the GD firmware and not the laser that allows for reading of GD data. I'm too lazy to dig up the topic, though. >= )

--MidnightObsidian

mariobro · Post by **mariobro** » Wed Dec 04, 2002 3:39 am

Damn.. the Dreamcast teardown report is gone... it was bound to happen...

The cool thing was, it was a FREE complete sample. That's why I recommended it. I don't do free advertising.

You can find the firmware stuff by doing a search with these terms: GD-ROM, Yamaha, Firmware, SDK, Utopia, Echelon, Kallisto. I can't give you the direct link, since those links are against the rules of this forum. But I'm sure you'll find it.

I'll check the DC PDF for info on the spindle motor.

Good Luck.

MidnightObsidian · Post by **MidnightObsidian** » Wed Dec 04, 2002 7:28 pm

Don't worry about the exact motor type. Just take one from a different CD player/drive, extend the wires, and mount it. It's not a hard thing to do.

sorewinner · Post by **sorewinner** » Thu Dec 05, 2002 9:53 am

Now THAT'S what I was looking for!

Thank you MidnightObsidian, and Mariobro!

Again, thank you Midnight. I knew if I kept it up, somebody would respond.

BTW, the teardown report isn't gone. The site just put it into their pay section.

MidnightObsidian, could you (or someone who archived the page) explain the deal with the firmware? There's gotta be something in the laser assembly which allows it to focus on the tighter tracks. A CD-ROM reader that can see up to 99 minutes does so because of its firmware, but that's because the track width is the same as a normal CD. A GD-ROM disc is actually written with a lower-wavelength laser, right? So anything reading that data would have to do so with a similar laser. Could you correct/expand on this, please? Thanks in advance.

sixteen-bit · Post by **sixteen-bit** » Thu Dec 05, 2002 12:07 pm

MidnightObsidian wrote: Virtually any motor will work, be it from a portable CD player, from a PC CD-ROM drive, or from whatever else. If it fits and it spins, it'll most likely do.

Yes, as long as it is the same / similar voltage and as Midnight says, it fits it should work. Don't worry about silly things such as spinup time or rotational velocity, as from my experimenting that does not seem to matter too much; though if you have a hella slow spin speed FMV and BGM starts to skip and go ghetto on you sometimes (and your game seems to take longer to load)

sorewinner · Post by **sorewinner** » Thu Dec 05, 2002 12:24 pm

Thanks for your input. Do you think that pulling the motor from a 12x reader should be an electrical match?

Pong · Post by **Pong** » Mon Dec 09, 2002 12:30 pm

Sorewinner,

Actually there DOESN'T have to be anything that allows the laser to focus on smaller tracks to read GDROM's. As MidnightObsidian suggested, the only difference is in the GDROM firmware. Otherwise, it's a standard 12X CDROM drive.

What most people don't know about CDROM's is that they actually hold on the order of 2GB. That's right, 2 Gigabytes! Now you're thinking "this Pong guy is full of it!". But wait... I'm not kidding. The reason you can only store 650/700 MB on a standard CD is that all that remaining space is used by the Reed-Solomon error correcting code to redundantly store that same 650 MB of information that the CD is supposed to hold. Without this redundancy, the smallest scratch would cause permanent data loss.

The theory I have heard, and believe to be true, is that Sega modified the error correcting code of a standard CDROM drive to create the GDROM drive. This allowed Sega to use an extremely cheap standard CDROM drive to read custom media with only a modification to the drive firmware. Very smart idea. This modified ECC used a lower redundancy factor allowing for more data storage using the same bit/track density as a CDROM. The only problem with this approach is that it theoretically makes GDROM's more sensitive to scratches and dust than standard CDROM's.

Scott

sixteen-bit · Post by **sixteen-bit** » Mon Dec 09, 2002 1:12 pm

Pong wrote: The theory I have heard, and believe to be true, is that Sega modified the error correcting code of a standard CDROM drive to create the GDROM drive. This allowed Sega to use an extremely cheap standard CDROM drive to read custom media with only a modification to the drive firmware. Very smart idea. This modified ECC used a lower redundancy factor allowing for more data storage using the same bit/track density as a CDROM. The only problem with this approach is that it theoretically makes GDROM's more sensitive to scratches and dust than standard CDROM's.

That is the theory I looked into a while back and I believe it is true. I first became aware of an "issue" with scratched DC games as the gamestore I worked at had many DC games with minor scratches that refused to load at all where we had, for example, PSX or PC games that were almost trashed play perfectly. I don't know the exact technicalities of it all but I believe the GDrom format (or should that be "hack", since it really is just a hacked CDrom format?) has minimal error checking / correction capabilities.

mariobro · Post by **mariobro** » Mon Dec 09, 2002 5:59 pm

Yup, GD-ROM is not some new standard or anything; it's just a clever CD-ROM hack. I remember reading this on a site by a guy who claimed he had worked For Yamaha and Sega, and showed pictures of his very own Dreamcast SDK. He said that it was a firmware thing. He also calimed to have a Yamaha CD-ROM drive that could read DC discs.

He remarked on the lousy error correction implemented for GD-ROM, which could render slightly damaged discs completely unplayable.

He also talked about spinning speed, CAV and CLV, regarding the Dreamcast GD-ROM drive.

He appeared to be tight with members of Echelon and Utopia, he even had an interview with one of those guys on the site.

Sadly, the link is dead. It was very informative, though.

sorewinner · Post by **sorewinner** » Tue Dec 10, 2002 10:43 am

This has now turned into the most informative Dreamcast-related topic I've ever read. Thanks, guys.

Pong, are you serious? You're saying that a CD generally uses a ~6.5/10 ratio of error correction data to actual user-written files? Geez. Is the algorithm used devised when the CD was actually invented? You'd think a more efficient one would've been implemented before the CD took off.

On a related note:
Since hacking the firmware to enable increased storage space makes the resulting disc unplayable in any non-modified reader, why would Sanyo bother to shrink pit size on their HD-BURN technology (seen here), when they could've just rewritten the firmware to handle the different error correction algo? Doing so makes it so that only firmware-modified DVD players can read their discs, not CD players. Any thoughts?

Pong · Post by **Pong** » Tue Dec 10, 2002 3:34 pm

sorewinner,

I can't quote the exact usable/total data ratio, but I think you're close. Many people assume that the laser is capable of reading past dust, scratches and other problems on or below the surface of the disk. Actually, the laser can't reliably read past anything like that which is why the data has to be redundantly recorded in another location on the disk (the ECC codes) so that it can be recovered in the event of an error. I've read material suggesting that the average CD reader experiences read errors about 20 times per second and is capable of correcting errors at a rate of 200 per second! The maximum length for a recoverable error on a CD is 4000 bits! That data has to be somewhere else on the disk in order to recover it. The reality is that even a scratch-free CD containing only 1 copy of each bit of data (no ECC coding) would be impossible to read without many data errors.

The ECC coding used on CD's is actually quite advanced and was the topic of a great amount of research before CD's became a viable consumer technology.

Scott

sorewinner · Post by **sorewinner** » Tue Dec 10, 2002 5:07 pm

Wow.

Pong, thank you for the lesson on CD tech. The same "thanks" goes out to everyone who posted in this very informative (to me, anyway) thread.

farrell2k · Post by **farrell2k** » Thu Dec 12, 2002 6:00 pm

On normal CDRs, 14% of the disc is used for error correction.

How did that spindle motor swap go? Did you ever do it?

sorewinner · Post by **sorewinner** » Fri Dec 13, 2002 10:52 am

Heh, not yet. Can't spare the time to search spare-parts stores less than 2 weeks before Christmas! It's been busted since September 2001, so I'm not in a huge rush. I should have it done by the end of January, though. Thanks for asking.

14%? That seemingly contradicts what Pong explained. Could you expand on this, please? Is the ~6.5/10 data-to-whatever ratio still valid? I say "whatever" because if 14% is for ECC, there still should be ~20% left for something other than user-written data.

Edit: Just visited your website. Very nice! Hope you don't mind some constructive criticism, though . Your guide to booting copied games in a non-modded console is good, but you should warn that your glue method will make it difficult, if not impossible for some people, to switch discs in multi-disc games like the FFs. If you have a solution for this, please post it here, since I can't come up with one, aside from breaking the glue and re-raising the depressed button. Also, what was your reason for switching analog sticks on the DC's and PSX's controllers? I take it you don't like, or prefer, the PSX's to that of the DC?