PowerComputing PowerTower Pro Project

Note – This Project is ongoing, and so this page will be updated in a very untimely manner as I undertake and document additional work on my PowerTower Pro.

Background

For a long time I have wanted a Macintosh Clone, basically because they came in more rugged cases and the power supplies should be easier to replace long term (which isn’t as true as I thought it was). Unfortunately, prices went up significantly and I haven’t been able to justify buying one, but recently I saw a PowerComputing PowerTower Pro 225 for sale “not working” on eBay. It was pretty rough with lots of missing parts and some dents and scrapes, but I picked it up as a project.

Condition on Arrival

• The original CPU is missing and a 9600/200 233 CPU has been fitted. The original part would have been a 225MHz PowerComputing part.
• Sadly the Level 2 Cache is missing – this is really unfortunate as the original part will have been a 1MB part, which are hard to get hold of. I don’t anticipate I’ll ever be able to replace this.
• The 80mm rear case fan is failing.
• The 80mm CPU fan is missing.
• The CD Drive does not look like the original part, and I suspect is a slower replacement. I haven’t tested whether it works yet.
• No hard disk fitted.
• One 5.25″ bay plastic cover is missing.
• The light pipe for the power button is broken.
• No video card (stock it would have been supplied with a ixMicro Twin Turbo (8MB version I think) or an ATI Rage II of some description I believe? I need to double check.
• The PSU is missing
• There is a single 64MB RAM module fitted. Given the computer interleaves RAM, it really should really have a matched pair, I anticipate it probably originally shipped with a pair of 16MB modules. This is more frustrating that I realised because I seem to have run out of my stockpile of 5v 168 pin RAM modules. I might have to downgrade another computer, which is always a shame.
• A number of screws and PCI slot covers are missing (and the ones that are there don’t match).
• The case is a bit beat up, as well as being dirty and the paint scratched, there are a few dents and panels don’t quite align properly.
• The logic board has been re-capped. They don’t appear to have cause any actual damage, but some rework might be good to tidy things up a little.

Given what is missing, I suspect this was a tricked out machine at some point – I suspect it had a number of PCI cards, much more RAM (otherwise there would be matched pairs and the original factory modules would still be there) and I suspect it had a processor upgrade.

The seller stated that they had tried powering it on and it did not chime. On arrival I sprayed contact cleaner in all the slots and undertook a general inspection.

The Plan – Subject to Change

Other than actually debugging and repairing, the following are what I plan to do with this machine to set it up as a usable and useful machine.

Short Term

• Find and fit a suitable PowerSupply.
• Fit a period video card, or one that represents a small upgrade. I’ll either fit an ixMicro TwinTurbo or ix3D, or alternatively I might fit a Radius ThunderColor.
• Install a PCI SATA card. SCSI hard disks are expensive, this lets me use a SATA DOM or similar instead.
• Replace the loud and missing fans with quiet modern fans.
• Add a second optical drive, probably SATA, to hide the missing bay cover.
• Fit a G3 upgrade card, probably something around 300MHz. I have a 300MHz green (i.e. not purple) Sonnet upgrade that might suit it.
• Knock some dents out and straighten the case.
• Clean the case.

Long Term

• Repaint the metalwork to solve the battered look.
• Work out how to repair the deep scratches in the front plastics.
• Rework the capacitors that were replaced to clean up the soldering and put them on straight, as well as check for any damage.
• Clean up the floppy drive internals.
• Fix the Power LED.

Progress

Getting it Booting

As I’d been told that it didn’t chime, but the CPU did warm up, I decided to try booting the absolute minimum. I couldn’t find a proper ATX power supply, so given I didn’t have any disks and only one RAM stick and no video card, I used my picoATX and a 5A 12V power supply – this is only 60W, but given the 233MHz 604e (System 7.6.1 reports it as a 200MHz CPU, but the part number and Clockometer agree that it is a 233MHz CPU – this is nice because it is the fastest Apple 604e, and a smidge faster than the stock CPU) fitted would only need less than 10W, I figured the remaining 50W or so was plenty for the chipset and fan.

Pressing the power button, the fan came to life, the floppy drive clicked and the CPU and things on the logic board warmed up without getting excessively hot. I powered it off and poked a non-bootable floppy disk in the drive to see what it would do… it tried to read the disk and then ejected it. This is extremely good news. It means that the computer is executing code from ROM and trying to find an OS. I powered down again and plugged in my stereo amplifier and speakers.

Yay! Seems that it does chime, just not through the internal speaker.

I grabbed a VillageTronic MPDD+ PCI video card (because I suspect it probably doesn’t use much electrical power) and popped it in the bottom most PCI slot. Plugged in a keyboard, mouse and VGA monitor and powered the computer on…

Promising… I found my ZuluSCSI Pico and plugged it into the external SCSI port and it booted right up. I didn’t hang around long, I just booted and checked System Profiler (I wasn’t certain what speed the CPU was, or how much RAM was installed, so now I know it is a 200MHz 604e (update – I thought I did, but it is reporting incorrectly based on the multiplier and it is assuming a 40MHz bus, the CPU is actually running at 233MHz on a 46MHz bus) and 64MB). Given I didn’t have a proper power supply installed, I shut it back down.

Removing Dents and Straightening the Chassis

There were two dents from point impacts in the side panel. I removed these by placing the side panel on top of a piece of wood and then hitting the inside (high spots) with a rubber mallet. This worked surprisingly well, the case is made from an extremely ductile grade of steel.

The case stands on four large feet, someone had managed to bend the case between the front and back feet so that there was an arch in the bottom of the case. I straightened this by hand, again, it bent back surprisingly easily.

Some of the side panel latches were bent out of shape. I adjusted these back closer to their original shape using a pair of small pliers. Don’t over twist them as it feels like they would break if worked too much.

I also used the mallet to adjust the overall shape of the case a little as it wasn’t quite square. If you do similar, obviously take care, perhaps remove any hard disks first.

The Next Day – Power Supplies, Fans and Sound

After getting my hands on a cheap next day delivery power supply I found that the power socket on the back wasn’t low enough to fit. I was already worrying about the fan position, as like most modern power supplies it has a large 120mm fan in the “top” as orientated in this case.

For now I just used the power supply with it placed on top of the case, with the case on its side for a bit more testing. While I was at it, I replaced the rear exhaust 80mm case fan with an 80mm Noctua fan. It fits, and the provided 3 pin cable matches the logic board fan connector. The only issue is that the existing fan guard doesn’t clip into place due to the mating material being a little thicker on the Noctua. This means that it is a friction fit instead of being held fast by the clips. This will do for now, but I might come back to it later. I don’t want to glue it because I want to be able to replace the fan again in the future.

I had looked at the internal speaker and cleaned the contacts where it connected to the logic board, but it still wasn’t chiming. After removing the speaker and holding it to my ear, I could hear that it clicked when the computer powered on. Before doing anything more complicated or costly, I thought I’d check the basics…

So… it turns out that the PRAM on this computer defaults to the built in sound being muted (I’ve had the battery out). Either that or it is falsely detecting that something is plugged into the external port (I’ve since investigated and I believe the issue is with the rear port). I un-muted the Built-in sound and…

Bingo, turns out sound does work. Mostly.

I left the computer running for about half an hour – it is so quiet I almost can’t hear it, which is bliss compared to most of my vintage machines. I’ve decided that I want to keep it like this and so have ordered an extra quiet 80mm fan for where one is missing for the CPU, and another to fit into the power supply I will end up using.

I noticed that the computer threw an error and crashed while sat idle. I don’t know why yet, but my first suspicion is that perhaps someone has removed the heatsink from the CPU and broke the thermal paste bond between the CPU and heatsink. Hopefully it isn’t anything too difficult to fix – I’ll come back to it and do some load testing with TechTool.

Onto finding an appropriate power supply…

The requirements for a power supply for the PowerTower Pro are as follows as far as I can see :

• The fan must be in the rear face of the power supply, and flush.
• There must be no power switch or LED sticking out (looking at you HP).
• The IEC power connection must be low down, and not vertically orientated.
• The internal power connectors must be compatible with 20 pin ATX and preferably have several “Molex” 4 pin 12v/5v connectors for powering drives.
• The power supply must provide 3.3v, 5v, 12v and -12v.
• Macs and clones from this era heavily rely on 5v. This is unlike more recent power supplies which provide more 3.3v, or even 12v for the latest models. Finding something that can provide over 45A for 5v like the original 9600 ~400W power supplies is almost impossible and so some compromises need to be made.

After several hours looking at power supplies on eBay, I decided that I wanted either an FSP300 or FSP350, specifically the PLT variants as these have stronger 5v rails than most power supplies. Additionally, the power connector and fan are in the right location, and I was able to find one for sale for a reasonable price. I ultimately bought an FSP350-60PLT, with a 5v rail capable of providing 32A.

The following shows the ideal arrangement of power socket, fan and no vents on the top surface (the one I bought does have vents in the top, but I’m hoping that there are more vents elsewhere, or that it wont be enough of an issue to matter) :

My PSU hasn’t arrived yet, so I am waiting on that and the additional two 80mm fans.