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The Source for Mac Performance News and Reviews

Your First BIG Case!
By Paul J. Tetreault, Jr. 1/30/2000

How to Use an ATX Case for External Drives or PCI Expansion Chasis
and Port Your 8500's "Internal" SCSI Bus Out to it - Page 2

Preparing the ATX Case - Jumpering the Power Supply

The Q500's 300 watt power supply has an on/off switch on the back of the case, but if you just plug the power supply in and press the switch you'll be disappointed, it won't come on. To get the power supply to switch on you must jumper a wire on one of the power leads, but please note this caveat:

This procedure applies only to the FSP300-60GT model power supply! If your connectors differ you will have to research the right procedure with your case manufacturer. You assume the risk in performing this procedure and neither XLR8YourMac nor I can be responsible for your results.

Take a look at the leads coming out of the power supply. Several have the standard 4 conductor connectors used to power hard drives that supplies +5 and +12 volts and two ground conductors. Two leads are different, they are the power leads that connect to a PC motherboard. One of these is larger than the other. The larger lead contains 20 conductors. Each of these conductors corresponds to a voltage level or gound in accordance with the color code printed on the side of the power supply. One wire, the only green wire on the 20 pin lead, is not listed on the color code.

Be sure the power supply is switched off (the "0" label on the power supply switch is depressed). Strip both ends of a short piece of hookup wire and insert the ends into the holes on the 20 pin connector that correspond to the green wire and the black ground wire next to it. Be sure the ends of the hookup wire are securely in the holes on the 20 pin connector and won't fall out. Turn the power supply switch on (the "1" label on the power supply switch is depressed) and voila, you should see the fan on the back of the power supply begin to spin. If you test the conductors on the power leads with a DC volt meter you should see you have the +5 and +12 volt signals necessary to power drives in the enclosure present.


The FSP300-60GT power supply supplied with the Q500 is quite rugged. It is internally fused and can handle a direct short across its outputs. Still, be sure the power supply is turned off before you jumper the green wire. Full specs on the PS are available here, including an MS Word file with even more detail.

Installing the Internal SCSI Ribbon Cable

The internal SCSI ribbon cable connects from the backplane of the ATX case to the drives you install in the ATX case. At the backplane, you will attach the first connector on the cable to one of the L-bracket "box headers" that converts from Mini DB 50(F) to 50-pin IDC(M). The L-bracket will slide right in to one of the slot openings on the ATX case's slide-out motherboard drawer. You can tell which connector is the first connector on the internal cable because it is separated by 18 inches from the next closest connector. Every other connector is spaced 8 inches apart.

But how do you know how to install the internal cable into the L-bracket connector? The connectors on the internal cable from GT Computers in the parts list are not keyed, so you could make a mistake. Here's the trick. By convention, the single red wire on one side of the ribbon cable corresponds to pin one on the SCSI bus. That means the internal cable should be installed so that the red wire is on the right side of every drive or L-bracket connector, just as the picture shows.

But here's the catch, to keep the red wire on the right side of every connector you plug the internal ribbon cable into, you MUST TWIST THE CABLE between the backplane connector and the first drive. This is because the connector on the backplane and the connectors on the drives face in opposite directions.

If you're using the recommended components, you'll see that the L-bracket connectors are labeled which pin is pin one. The internal ribbon cable is constructed to be attached to drives starting at the top of the ATX case and working downward. If you want to attach to drives from the bottom of the case to the top you'll need a different cable with the 50 pin IDC connectors attached on the opposite side of those on the recommended cable. This might sound confusing but it all becomes clear when you start hooking things up. If you need a custom cable, Granite Digital can help you out, but you'll pay at least $150 - more than all the other components put together - for it.


Orient the internal SCSI cable so the red wire on the female 50 pin IDC connector attached to the cable plugs into the RIGHT side of the male IDC connector on every device or L-bracket connector.

Porting the 8500's Internal Bus Out of the Case

Thanks to the Proline third bay removable kit, porting the internal SCSI bus out of the 8500's case is no sweat.

Step 1 - To start, remove any internal hard drives in the third and bottom bay of the 8500 - just leave the CD and the floppy. You can install your old hard drives in the ATX case.

Next, route the 8500's internal ribbon cable into the third bay, making sure it can reach to the front of the bay. If the cable is too short to reach, attach the 5 inch extension cable that comes in the Proline kit.

Step 2 - Next we'll attach one of the "box header" L-brackets to the metal drive bracket attached to the sled in the Proline kit. Place the short leg of the L-bracket on the outside edge of the vertical wall of the drive bracket as shown. Check the orientation of the Mini DB 50(F) connector. I matched up the orientation with the orientation of the L-bracket on the backplane of the ATX case so that the 3 foot external cable that runs between the 8500 and the ATX case did not have to twist.

Mark the long leg of the L-bracket where it meets the vertical wall of the drive bracket on the other side of the sled. Using this mark as a guide, you'll bend the long leg of the L-bracket so that it fits outside the vertical wall of the drive bracket just like the short leg does. If you bend it wrong the first time straighten it out and try again. Nothing will show when your're done!


Step 3 - Slide the Proline drive sled into the 8500's third bay and attach the 8500's internal SCSI ribbon cable to the 50 pin(M) IDC connector on the back of the L-bracket. Remember, red wire to the right. Take a look at how the internal ribbon cable attaches to the 8500's CD and just pretend the connector on the sled is another drive - connect it just like the CD is connected.

Step 4 - Replace the 8500's case cover and check your fit, if necessary you can raise or lower the L-bracket by attaching it to the upper or lower grooves in the vertical walls of the metal drive bracket. I found the upper grooves worked best.

Snap the bezel that came with the Proline kit in place. At this point you can attach the external Mini DB 50 terminator and power up your 8500 if you want.

I finished up by cutting out a piece of the trash can (remember the trash can?) just large enough to cover the rectangular opening in the bezel - it's about 1 x 4 inches. Using an Xacto knife, I trimmed a slot in the trash can material just large enough for the Mini DB 50(F) connector on the L-bracket. The beige trash can plastic matched the color of my 8500 case perfectly (no comments from G4 owners, please!) as you can see from the picture of the finished project on page one of this article.

Remember, a narrow SCSI chain needs to be powered up before you turn on your computer, so turn on the ATX power supply before you boot. I also found I had to play nice and eject the CD in the CD drive installed in the ATX case before I shut down or the CD would not mount on the desktop the next time I started up.

The only thing left to do is go out and buy all those new drives you've been craving. But remember to buy the internal versions - you won't need to pay more for an external drive with its own enclosure after this project!

If you've got questions drop me an email at pault86@erols.com, I'll be glad to help if I can. After all, isn't Apple users helping each other why there is an XLR8YourMac in the first place?


Step 1. Take out the 8500's internal hardrives leaving just the CD and floppy. Pull the internal SCSI bus cable to the front of the third bay.



Step 2 (a and b). The short leg of the L-bracket has a screw hole that allows it to be attached to the top groove in the vertical wall of the drive bracket. The end of the long leg is notched, so you can hold it in place with large washers. Don't worry if the L-bracket mounts at a slight angle. The Mini DB 50(f) connector is so short any angle will not really be noticeable. You can disassemble the 50 pin connector from the L-bracket to orient it the way you want so your external cable doesn't have to twist.



Step 3 Attach the 8500's internal SCSI cable to the Proline sled and bracket assembly. Slide the sled in until it locks in place.


Step 4. Attach the bezel that came with the Proline kit. If you want, you can glue a piece of beige trash can material - or any other material you like - in the opening of the bezel, trimming a slot for the Mini DB 50 (F) connector on the L-bracket.



<-- Back to Page One

(If you missed it previously, check out our past article on
converting an 8500 to a PC ATX Case.)


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