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Troubleshooting my Mac IIfx
by Steve Wood
April 10, 2000

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I found a loaded Mac IIfx a couple of years ago on an eBay auction that I just couldn't resist. The IIfx is the granddaddy of the venerable Mac II series. Marketed from March, 1990, to April, 1992, for a cool $10,000, it blew the socks off of anything around.

The Mac IIfx was the dream machine of early 1990's graphic artists. It blazed at 40 MHz, had six NuBus slots, eight RAM slots, and room for one hard drive and two floppy drives. It used several advanced features, including a faster data transfer system that required some special termination of the SCSI chain, both inside and out.

Mac IIfx in classroomThe one I purchased set me back a bit, as it came loaded with 68 MB of RAM. The Mac IIfx is the only computer I know that uses 64-pin SIMMs. (LaserWriter IIntx printers also use the 64-pin SIMM.) The 64-pin SIMMs are hard to find, and the cost of 64MB of new RAM, if you can find it, is far more than I paid for my entire IIfx! 18004Memory.com still lists 16MB modules in sets of four, but get ready to gasp when you see the price! MemoryX and We Love Macs also list 1 and 4 MB 64-pin SIMMs for the IIfx.

At any given time, there may be a wealth of IIfx parts and computers available on the eBay auction site. While it's sorta sad to see the old machines going so cheap, I opted not to write this column on my IIfx, which is recovering from unnecessary major surgery! While some functions are still quite fast, it is a 68030 chip computer.

My IIfx has been anything but untroubled. While an outstanding performer when it worked, it was subject to random hardware crashes at least once a day. I'd pretty well ruled out software problems after disabling most of the likely culprits and having run TechTool Pro, Norton Utilities (3.5), and Conflict Catcher a bunch of times. At other times, it just refused to start until bopped or torn down and reassembled. The addition of the proper external SCSI terminator solved some of the problems, but the day finally came when it refused to start despite my best efforts. A final complete teardown by some of my sixth graders, including removal of the motherboard and re-seating of all of the RAM and ROM chips, bought it two final, untroubled weeks of use. Then it went down again and stayed down.

Rather than continue to fight the critter, I took the fx home and replaced it with the Mac IIsi we use in my classroom as a spare. The IIsi has been a consistent, stable performer in its role as a backup machine. While slow, it has Ethernet and even runs CDs from our ancient JVC CD burner.

I just let the IIfx sit a few weeks while I found a replacement motherboard on eBay. It came in a box over twice the size of the motherboard with enough bubble pack to keep my daughters merrily popping for a week! When installed, the IIfx fired up and ran like a champion...for about 15 minutes. The machine would start and run a bit and then stop. On restarts, it often would display a gray screen and halt, or not engage the monitor at all. I swapped video cards. I swapped video cards again with no improvement.

Power supply screw Balcony screws Screws (red) and catches (green)

Pulling a motherboard on a IIfx isn't really a difficult chore. First, when the unit is off but still plugged in, tap the power supply to discharge any static electricity. One spark onto almost anything could ruin your and the IIfx's whole day.

Unplug the unit. If you're going to pull the power supply, there's just one retaining screw. Remove it, unplug the supply from the motherboard (There's no catch or lock on it.), and pull the unit towards the front of the machine and then up and out.

Four screws hold the "drive balcony" in place. Unhook the cables attached to the drives and then remove the four screws. I remove the screw closest to the floppy drive last, and remove it with the balcony. Otherwise, a screw usually falls on or under the motherboard.

The motherboard is held in place with two screws and (let me count) nine nasty but effective plastic catches. Remove the screws and start loosening the catches from the front to the rear of the motherboard. Then work the motherboard out. You'll need to go back and keep re-releasing the nasty, but effective plastic catches.

I finally consulted the Apple service manual and found that the internal SCSI filter should be mounted on the hard drive, rather than on the motherboard SCSI block, as the machine had come to me. This little gem may help in the future, but it didn't prevent the IIfx from sounding the "chimes of death" repeatedly. It's also necessary to carve off the edge of the power plug so that both it and the filter can go into the hard drive side by side (see left photo below).

Trimmed plug Internal SCSI Terminator Plug and filter on hand drive

I switched power cords as suggested in the service manual. The manual also had a note about an auto shutdown feature to prevent overheating, but that really didn't seem to be the case, unless there was a bad thermostat involved and duplicated on two sets of parts. I would have switched batteries, but I'd put in new ones with the motherboard swap (not an absolute guarantee, but close.) Unnerved but undaunted, I rearranged and re-seated the RAM chips. Then I switched power supplies--twice. At that point, I done everything but swap the RAM, which I'd tested with TechTool Pro. Had I been a little sharper at the time, I'd have run the old utility, Snooper, but I never thought of it.

After several hours of futile attempts at repair, I finally took a break and watched All the President's Men. This has nothing to do with Mac computing, other than it probably saved the IIfx from a quick decent out a high second story window.

When I resumed my troubleshooting efforts, I also decided to try to set up OT/PPP and a modem during the machine's brief periods of activity. As I started to type in the name of my internet service provider, I noticed the "G" key was dead. For some folks, this would have told them the answer, but I'm still using a keyboard at school for the MacServer (Power Mac 8550) with a dead "x." I eventually grabbed another keyboard and for good measure used a brand new cable that I'd found in a box of junk at school.

While generally fooling around waiting for the proverbial cartoon lightbulb to appear above my head, I saw all three keyboard indicator lights (num lock, caps lock, and scroll lock) flicker on and off. I jiggled the mouse connection and the lights flickered again...and the mouse went dead. The keyboard, it turned out, was deader than a doornail as well. Fortunately, I had one more keyboard to try before I had to start pulling them off working Macs in the household.

With the "new" keyboard, the IIfx refused to lock up, even when I flirted with disaster by using an external ZipPlus drive without the special external terminator (which I'd left at school). I'm still not sure whether there was something else wrong with it that got knocked back in whack with all of the in and out of parts. I can't imagine having gone through three bad keyboards (counting the one at school which is working fine with the Mac IIsi). But apparently, the IIfx was locking up at startup when it did its startup hardware check. When it found a bad keyboard, it gave the chimes of death.

At any rate, now I'm "stuck" with an extra IIfx motherboard (grin, grin) that I guess I'll just have to drop into a Mac II case and use at home!

Update 10/9/2000:

In September the "cured" IIfx again began to sound the chimes of death from time to time. A good whack on the side of the case usually restored it to operating condition, but that didn't bode well for the internal components.

Reader Ken Creppin suggested that corrosion on the ROM SIMM connectors and slot could be the culprit. He'd had success using "flux remover for PC boards" to correct the problem on a IIfx. While I didn't have any of that solvent, I did have some Brasso. Sure enough, the IIfx returned to life. A similar treatment to the extra IIfx motherboard also worked and it went into a Mac II case to become a IIfx "sleeper!" (Remember in your youth when you got blown away by a sleeper Chevy Nova, only to find out later someone had dropped a 327 into it?)

Thanks, Ken!

Some places and things that may or may not have anything to do with the Mac IIfx:

Odd thoughts while shaving between paragraphs:Power strip hog

Does anyone else but me get frustrated with peripheral power supply units that take up so much space that you can't use the plugs beside them on a powerstrip?

While just generally mucking about on the online auction circuit, I have been continually amazed at the quantity and variety of Mac IIs available. One of the really neat things about Mac IIs is the interchangeability of NuBus cards. A reader recently wrote that he was hunting Ethernet cards for his twin IIfxs and his 6 year old twin daughters! I suggested that if he couldn't find the Ethernet cards individually, he might consider buying a whole computer on an auction that includes an Ethernet card. I picked one up that way a couple of weeks ago when I bought another Mac IIcx. The cost of the entire transaction was about one-third of what an Ethernet card goes for new. But just think of it--twins on twin Mac IIfxs. Sounds like a Low-End Mac photo opportunity!

The sunroom Mac graveyard!When I started to put this column together, I found a photographer's horror. I'd done all the photo work without wearing my glasses! For those of you with good eyesight, that means I let the viewfinder act as glasses while focusing the shots, but also making the images blurry. So...the IIfx had to come apart again. As soon as I get done editing and sending this column to Dan (Knight), I'll get to put it together again:-). Annie hasn't noticed the mess I've created in the sunroom as yet.

I'd hoped to include a link for the Mac IIfx service manual, but Apple has closed or moved the directory! Once again Apple has "helped" Mac users by making it more difficult and more expensive to maintain their older Macs. I'm sure it must be to "improve the user experience."

Finally, if you were wondering about what happened on the Going WinTel...for a Month columns, Windows95 and the IEP program worked well all week. Whew! I still have one more week of solid Windows computing at school, but I just couldn't stand to write a column this week dealing mostly with Windows and Individualized Educational Plan issues.

Note: This column was originally published on Dan Knight's Low End Mac.

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last updated 11/7/2014
©2000 Steven L. Wood