Resurrecting an Atari 800

We’ve amassed a little collection of vintage computing hardware over the years — some owned and some acquired. On the shelf behind my desk sat an ailing Atari 800 that looked cool, but just would not boot up and that just bothered me. The time had come to see if it could be revived or relegated to becoming a bookend.

When it comes to vintage and retro home computing, I’m not an Atari person (I’m a SInclair/Commodore guy); that’s the realm of my significant other — the machine is hers from way, way back and was an attic re-gift from her mom. Her dad fixed the machine before, but then she went off to college, all of the Atari components were boxed up and stored away for about two decades. The intervening 20 years were not kind to the gear and something failed somewhere (again).

The first challenge was figuring out how to connect a vintage home computer to a modern monitor as RF switches are long gone and I no longer have any CRT-based displays. Fortunately, the Atari 800 came equipped with a round DIN multi-pin connector for AV, so a quick search online surfaced the right cable. Connecting it to our 46” Sony LCD TV wasn’t an issue as it still has composite video and analog audio RCA-style inputs, so I patched the connections to the TV according to the labels on the breakout cable. All good so far.

Next, I rooted around various boxes and I found the Atari power supply, plugged it in and hit the power switch assuming that the transformer worked. The red light came on, the speaker made a little blip noise and voila, nothing on the screen nor anything out of the TV’s speakers. I power-cycled it again and it started up, but nothing except a little static on the TV screen. It was at that point when it dawned on me that the breakout cable labels assume contemporary connection standards — but the Atari came out before those standards came into regular practice. I proceeded to work through various RCA cable combinations until suddenly there was a blue screen and beeps coming from the TV. We had audio and video!

Sadly, though, the excitement was short-lived. The boot screen started barely got through writing “Atari” and then turned to jibberish. Something was definitely amiss.

Next, I popped the cartridge and expansion card covers and reseated everything. No dice. The problem was serious. I unplugged everything, took the machine over to my desk and carefully removed the plastic covers. After the bottom cover was off, I gently removed the ribbon cable to the keyboard that was mounted to the top cover.A close examination of the motherboard revealed some corrosion and possible capacitor leakage. In short, the motherboard was likely dead. With a tinge of sorrow, I put it all back together and set the machine aside.

Fast forward several years and I found a re-capped motherboard on eBay. A quick order and a few days later, I had a rebuilt motherboard in my hands. This particular motherboard lacked a CPU and the Pokey chip, so I’d need to install those from the original machine and onto the new board. I disassembled everything again to reveal the electronics inside. The Pokey chip was relatively easy — there was a big empty IC socket on the new board, so I found the socket on the old one and using a thin flathead screwdriver, I gently worked the chip up and out. Being careful to record the orientation of the chip relative to its socket, I gently press-fit the IC chip into its new socket on the replacement motherboard.

The second task was to swap out the CPU. With this kind of machine, the CPU and part of the graphics subsystem is mounted on a card that plugs into the backplane of the motherboard. And because all of the hardware is sensitive to RF interference, the card is buried within a solid aluminum shield casing so when you look at the motherboard, you really can’t tell where the CPU is. After studying the assembly, I removed the very heavy aluminum shield from the old motherboard, which revealed a tight-fitting CPU card under the rearmost portion of the shell. I carefully pulled out the card (being extra careful about static discharge) and set it aside. I moved to the new board and removed its aluminum housing and inserted the CPU card and put everything back together. Confident of my workmanship, I put the machine back together.

By the way, when you move to a new home, things just are not where you expect them to be. In this case, the power supply was missing. Frustrated with myself, I did another quick search online and ordered a modern replacement.

A few days later, the power supply had arrived. In the meantime, I found the video cables, but had a new problem — I no longer had ready access to a composite video display. Undaunted, I dug out an old Elgato Game Capture HD interface, plugged the cables into the appropriate adaptors, fired up the iMac, ran the Elgato software and turned the Mac into an old school composite TV. With all of that running and the new power supply in place, I switched on the Atari.

The Atari 800 booted up properly but after about 15 seconds, it halted. Discussing the problem with the Atari expert in the room, we decided to try a different cartridge. In went Centipede and it started up fine, but after a while seized up. We popped in Ms Pac Man and at the exact same place each time we booted up the machine, it froze. Something wasn’t working right at a program execution level. After swapping in and out all of the RAM cards, we determined that memory wasn’t issue. The problem was likely at the instruction-level. Given that the original motherboard had issues, my gut told me that it was probably the CPU card. So back online I went and ordered a tested CPU card.

A couple of days later (again), the CPU card arrived and I went through the multi-step process of swapping out the card from beneath the massive aluminum shield. What I did notice, however, is that there were no pads on the new card to keep it from wobbling and accidentally coming into contact with the metal housing. A few turns of electrical tape later and a safety shield was in place. Satisfied that it would be electrically okay, I methodically put the whole thing back together for another test run.

Atari 800, check. Power supply, check. Video cable, check. Elgato video interface, check. iMac ready, check. Power switch on.

Well, it got further but still seized up. Something else was wrong.

We had replaced everything except the single power and IO board and the Atari OS 10k ROM. Power and IO seemed fine, so the only thing left was the base OS. Back to an online search, which uncovered a tested Atari OS card. A few more days later, it arrived.

At this point, hope was at an all time low. I was getting ready to start another flurry of work trips, so if I didn’t test it soon, it would sit for weeks. Just before bed, I pulled the Atari 800 off the shelf and hooked everything up. I popped in the Atari Basic cartridge and turned on the machine.

“Ready”

The machine didn’t freeze; it didn’t halt. It just sat there waiting for a command. I turned it off, popped in Ms Pac Man and turned it back on. It ran through its demo and didn’t stop. The demo does not have any audio, so I turned it off, popped in Centipede and turned it back on.

The demo started running and didn’t stop. It kept going with its digital soundtrack beeping away though my studio-grade speakers. It didn’t freeze for over five minutes.

“It’s alive! It’s alive! It’s ALIVE!” (insert a reference to “Weird Science” here…)

The Atari 800 is a working computer once again. Time for more retro fun.