Classic Restorations

Damaged Goods: A Quadra 840av Brought Back from the Brink

- 2006.04.05

How a shipping-damaged motherboard and an unloved 386 joined to create Damaged Goods, the World's Ugliest Quadra.

I hope that by relating this tale of giving new life to a dead Mac I can inspire others to do the same. When these vintage Macs are found, they've often been abused and neglected, but with some care they can be brought back to health and function. Even if you don't have money to spend on the repair, with time these great oldies can often be revived.


Every sordid love story has a humble beginning, and this is no different. Another vintage Mac user and I had decided to trade some extra equipment. Eventually, the postman had a present for me: two working ST34501W 4.5 GB Cheetah hard drives and a Quadra 840AV motherboard in unknown condition. Feeling excited, I tore into the package. Now I'd have everything I needed to finish research for my articles on Overclocking the Turbo 040 and System 6 Performance (coming Real Soon Now™.)

I hadn't expected the 840AV to work, but I needed a real 40 MHz 68040 chip. My plan was to grab the 40 MHz part and then ashcan the motherboard.

As the tape and cardboard gave way, I got a bad feeling. In shipping, the hard drives had migrated to the topside of the motherboard and there danced a fandango. The drives were a total loss, and the board was a wreck with broken and bent pieces all over the place.

I was very disappointed - but happy that at least the precious 40 MHz chip survived. I transplanted it into my Turbo 040 and continued my research while the forlorn 840AV looked on from the corner of my workbench. Sitting in such close proximity, I began to wonder if it really did work or not, and that's the start of our adventure.

The Rescue Begins!

Revivification first required a through looking-over to note all obvious problems. I used pliers to repair the bent metal and plastic, and with soldering gear affixed everything that had been knocked loose. I even amazed myself by reattaching a tiny leg that had been sheared clean off of a surface mount RAM chip!

I socketed the 33 MHz 68040 from my Turbo 040 and used thermal tape to affix a giant copper-bottomed Pentium III heatsink.

Noting that the main power connector found in later PCI Power Macs debuted in the 840AV, I connected the power supply from my Power Mac 7500, a keyboard, mouse, monitor, and speaker.

Pressing the power button yielded a startup "Bong" from the speaker, and then nothing. No gray pattern, no flashing question mark, just nothing.

To find out if it was just fried video or if the whole board was bad, I fitted a small SCSI drive with a universal System 7.5.5. I planned to listen to the hard disk to tell if it was doing anything.

With everything connected . . . the screen came alive and 7.5 started booting!

I tinkered with it a little more and then asked myself, "What am I going to do with this thing?" I had no case to put it in nor a power supply to run it - but I just couldn't junk a perfectly working Quadra.

Looking first to eBay, I found the going price of new power supplies too steep for my budget. I found the pinout for the 840AV power supply connector on Accelerate Your Mac; with it I could use any PC power supply, but I still didn't have one.

I remembered that my wife's parents upgraded from a 386 to a Pentium PC several years ago and just stuck the old machine in a closet. That would be my source! I asked for and was given a Magitronic 386 SX/40 in an ugly AT-style case.

Get ready, little Quadra, you're going to be moving in here!


The first step was to strip the chassis. Removing the 3.5" and 5.25" floppy drives as well as the 120 MB hard drive proved easy, but the motherboard was a challenge. The plastic mounting offsets that held it had gotten stiff and brittle with age and were extremely difficult to unhook. After bandaging a small cut I received in the process, I succeeded in emptying the metal 386 case.

Another problem: The bottom of the case had three ridges that stuck upward and could short out my Quadra if I left them in place. On this particular case they were held fast by pop-rivets, which were drilled out with an electric drill. There was a smooth surface on which to place the 840AV board.

The ISA slot cutouts in the case would have presented a problem if they hadn't been stamped into a large assembly and screwed into place. Removing a few screws allowed me to create a large hole in the back right-hand side for the ports and NuBus cards to peek out of. The ports still needed more room, and the metal case back gave way to a Dremel with a fiberglass cutoff wheel.

With the case prepared, a way to hold the motherboard was necessary to prevent short-circuit. The board was kept at a safe height by applying copious amounts of 3/4" stick-on weather stripping to the underside. Then its physical location was secured using duct tape. (A more permanent fix using plastic wire-ties is forthcoming.)

More than "Pure Imagination"

Using the case's built-in faculties to hold floppy drives, hard drives, and CD-ROM drives was easy, leaving the power supply hookup as the last major roadblock to having a functional computer. I had the AT-style power supply from the 386, but I needed a connector. To acquire one, I went down to my local computer wrecking yard and asked for a dead ATX power supply.

The Quadra power connector is just like an ATX connector but with an extra column of pins. It also has two "unused" pins that get no connection when doing a PC power supply conversion. Converting an ATX connector is as simple as cutting the last two pins off and plugging them into the Mac one column over. Then leave the two unused pins with nothing connected to them at all. Perfect!

I cut the connectors off the ATX and AT power supplies. Using the Mac and AT wiring diagrams, I wired the PC/AT power supply to the modified ATX power connector, plugged it into the Quadra, and fired it up.

It worked the first time.

Now only minor issues remained. The 386's speaker worked great and plugged right in. The Opteron light was easy to figure out using a multimeter. The Reset switch wires are soldered onto the built-in Power button. The disk activity light wires will eventually be soldered onto the permanent hard disk, and RCA jacks will be back panel mounted and wired to the video-in and video-out ports.

Damaged Goods is complete!

Putting It to Task

Every vintage Mac I own needs to have a purpose - otherwise it ends up getting buried under dirty clothes in the closet. What purpose has a Quadra 840AV?

I mulled this question for a few days until I realized that in my spare time I used to enjoy playing video games. Having quit Diablo II (after six years!), I was looking for a game to play, and I remembered that I had never finished Marathon.

I've acquired a Gravis Mac GamePad and puzzled out a good keyset for Marathon play. In the near-term, the 840AV's lease on life will be helping me battle the Pfhor. In the future, I'll use the built in video-out functionality to enable a portable retro gaming rig. I can show off classic Mac games like Marathon, Super Maze Wars, Bolo, and Harry the Handsome Executive. It can display on any TV - no monitor required!

Holding down cmd-opt-T-V during startup forces the 840AV to use video-out instead of the monitor port.

Powerful Software

Several pieces of freeware and shareware help to maximize the capabilities of this formidable machine, but they've become all but lost. James Wang's Quadra AV Pitstop website still has these valuable control panels and extensions.

  • Sound Effects - Cutesy demo to show off the power of the DSP by applying selected audio filters to everything the Mac puts out - in realtime. Macintosh performance is unaffected. Very interesting for Marathon, but I don't think I'll keep it.
  • AV DSP Power - Adobe Photoshop plugin that uses the Quadra DSP (digital signal processor) to accelerate Photoshop filters. A neat toy, but I'd rather have a Power Mac or a Thunder IV GX. The price is unbeatable though!
  • sAVe the Disk - This system extension takes the place of several (now lost?) Apple patches and also fixes some bugs Apple never touched at all. Most notable is a bug-fix that speeds up programs that play lots of sounds, such as games. Every time a new sound channel is allocated, the "DSP Preferences" file is updated; what this means is that every time you fire a shot in Marathon, your hard disk is accessed - that's crazy! sAVe the Disk fixes this problem and more!
  • Fix-Gamma - An application that launches, patches a bug that makes gamma-table changes look ugly, and quits. Great to drop into your Startup Items folder.
  • AV Digitizer Options - This QuickTime component adds support for the Quadra's many advanced hardware capabilities. Digitize color video in grayscale, use hardware chroma-key masking, and even blend digitized TV with your applications while you work. All these tricks are performed in real-time by the DSP, so the Quadra never slows down.


As you can see, bringing this Quadra back from the brink of disaster has taken a while! Now it has drive, purpose, and special software to help it work its best. The effort has been rewarding and fun; that's the joy of the vintage Mac hobby.

If you've got an AV Quadra or Centris and haven't tried watching translucent video while you work, you owe it to yourself to download the software and experience the marvel of these old machines.

Next time you see an old Mac languishing under abuse, think of Damaged Goods' rescue when all seemed lost. Don't hesitate to lift that fine computer from destruction and restore it to use. You'll be rewarded with a feeling of accomplishment, and the price is lower than buying on eBay.

But excuse me for now - a hostile craft is nearing our ship. "Somewhere in the Heavens, they are waiting...." LEM

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