Purple mini
Background
When the mini was first released I was kind of disappointed to learn it had a laptop drive. Slow, low capacity and expensive to upgrade! I did a little research and decided an adapter was needed. Since I could find none for sale, I designed one. My first project was to build a mini server in a PC case with two 250GB drives mirrored - kind of kludgey, as it used two power supplies and was way too big and noisy even at mini-ATX size. Shortly after I picked up a "mystic" G4 400MHz gig-E machine and since the mini no longer needed to do server duty I could revise the mini modification. This is the story of the purple mini.
Ingredients
The mini, obviously. A Maxtor Maxline II 250GB drive. A Panaflo 80mm fan. Some way to power the drive.
A table saw, router, scrollsa, angle grinder, some 2mm sheet aluminium, 12mm particle board and Marshall "purple levant" tolex amplifier covering.
Power
Without some way to power the hard drive I would be back at square one using an ATX supply again. Exploratory probing of the mini's circuit board didn't expose a convenient 12V supply and even if I had found one I would have been guessing about whether it could power the drive - rounding up, a desktop drive needs about 12V 1A and 5V 600mA. Linear regulators (LM7812, LM7805) are just within spec for this.
First you need an input voltage. The mini's brick can supply 18.5V at 4.5A and about 50% of capacity is used in a stock mini. So, no worries there, as long as I could get to it. More probing around the board revealed it wasn't available anywhere easy so I decided to go to the source, soldering to the back of the input socket. Removing this socket was difficult, and I needed to nibble away some plastic to get to the right pin (second from the back) but soon I had it back in the board with a wire on there and epoxy sealing it all up and providing mechanical strength.
The linear regulators didn't work - they got hot, even though I had used big heatsinks and the drive wouldn't spin up. I was thinking I would have to buy an auto-ATX supply (basically a DC-DC ATX power supply) when I remembered a Wiebetech firewire drivedock I wasn't using. These have a good power circuit and are designed to power 3.5" drives from bus power, they use quality National DC-DC regulators - problem solved. I cracked open the firewire interface and lifted off the convenient power board, adding connectors for fan and drive power at the output, a connector for brick power at the input.
The fan uses 7V, derived by using the 12V supply as positive and the 5V supply as negative. Powered this way the fan is all but silent - I can hear it, but any typing or music or pretty much anything else drowns it out.
Connections
Inside the mini the
drives connect by a daughterboard. This board connects via edge
connector to the mainboard, by 44-pin connector to the hard drive and
by 50-way connector to the optical drive. It also contains pads to load
components for an extra firewire interface but that's outside the scope
of this guide. The problem is to connect a normal 40-pin hard drive to
the mini, assuming it has a normal IDE interface (it does).
This is the adapter - it just translates pin 1 to pin 1, pin 2 to 2, etc. etc. converting the 2mm-pitch 44-way connector to the 2.54mm-pitch 40-way connector desktop drives use. The adaptor to do the reverse (connect a lptop drive to a desktop machine) is common, but I could not find any place selling what I needed. You can see in the picture that with standard drive removed, a ribbon cable can exit between the memory and optical drive and connect a desktop drive jumpered as master.
I opted to keep the standard Superdrive in my mini because I like slot load and I did not have a better drive available. You could of course use any optical drive, since the IDE bus that the adapter exposes will support two drives provided they are jumpered right and that your cable has two connectors. You might need to resort to a software solution to get optical drives burning properly if they are not a model that Apple has shipped, but just about any drive will work.
Cabinetwork
As you see from the pictures the base is just a piece of particle board with various router cuts in it. To keep the case as low as possible there are recesses for the 80mm fan - the board is 12mm, the fan 80mm but the height of the case only 90mm. Also there is a square recess for the rubber base of the mini to sit inside, providing a secure mount with only two hold-downs. The drive mounts (rubber, vibration-absorbing) are recessed also to match the depth of the fan recess and to avoid having to find abnormally long 6-32 mounting hardware.
The top of the case is a simple U-shaped construction with 12mm particle board, to which I added front and rear panels made of 2mm aluminium. The rear panel took longest to cut since it needed a rectangular hole for the mini's rear panel, a fan hole and a "step" running almost the full length to accommodate the fan recess. The front worried me for a long time - how do you cut a CD slot in aluminium unless you have a milling machine? Finally I set up a secure fence for my router, slowed it down as far as it could go and used plenty of cutting fluid. In two careful passes I got the perfect slot.
Covering the case was a lot easier than expected. I've got a guitar amplifier project going at the moment too and in shopping for vinyl covering I found this purple stuff - apparently Marshall produced some limited edition stacks for Jimi Hendrix covered in this material. I think it's a great color! It sticks down easily with 3m 77 spray adhesive or similar and once rolled down well it's stuck for good. The excess can be trimmed off easily with a sharp blade, i.e. scalpel or NT Cutter. I expect it is going to be durable and acoustically quite dead.
Finished
Here's the final product. If you look carefully you can see two problems. One is that there is no gasket behind the slot-load opening - I need to make one once I find some suitable material. By cutting a piece of material large enough to cover the slot and then cutting a slit with a knife it should be possible to make a tight-fitting gasket just like the original. Then a little glue will hold it to the inside of the case. This won't help all that much but I can feel just a little breeze coming out of the slot onto my left hand. Second problem, under the rear of the mini you can see some bare wood - my fault, I should have left that section unrouted and covered it with vinyl too. Eventually I will cut a little piece of wood to go in there and add a small piece of vinyl to cover it up.
This new arrangement is a lot faster than a standard mini. Apart from the slight speed bump from clocking it at an even 1.5GHz and adding 1GB RAM, the 7200rpm 8M cache hard drive is really much faster. I like to be able to hear the drive but not too much of it - when it's working I want to know but I don't want it to bug me. This is perfect. Finally, the only time I have heard the mini's CPU fan spin up is while looking at the newly released demo of "Darwinia" - the case fan seems to be pushing more air through the CPU cooler and that generally this machine is running coler than a stock mini.
The adapter to use a desktop drive in a situation requiring a laptop drive is available from me, you can mail me at hotmail.com (aeberbach) for all the details.
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