How I Spent Maai Weekend

My friend Tim Schutz and his malfunctioning robot Maai came over for our third Robot Sunday last weekend. (Robot Sunday one, two.) We’re trying to restore the robot, a Heathkit HERO-1, to full 1980s lustre. Maai was wearing a kind of clown mask Tim made to replace its protective faceplate, and an elastic belt to keep its panels on. On boot, the robot said “Low voltage”. (This was to be a recurring motif.) Then Tim demoed adjusting the pitch and speed of Maai’s voice.


Last time, we hypothesized a couple of chips had to be replaced on the main sensor board. Tim had bought the chips for our proposed repair from Alphatronics USA in the Tukwila warehouse district near Seattle. Entering the store, he said, was like entering the twentieth century.

Concerned about the voltage, Tim checked it on the robot power supply: 5.3 volts, so probably OK.


The robot was plugged into the wall, because Tim didn’t charge it the night before; he left the robot in the car all night…


Bad robot, no chips. Well, OK, a couple – Tim yanked the sensor board, I replaced the analog-to-digital chip and one other, and Tim replaced the board.

It was now time for diagnostics, as many diagnostics as the galaxies in the sky. Fortunately, we had the arm and pendant (wired remote) this time, and Tim and I were both getting the gist of the diag routines through the sheer rotework of entering them in hexadecimal machine language over and over.


We got through the initial diags to the first sensor tests (motion sensors), but then once again, no response. The LEDs were supposed to light up on motion. (As we worked on Maai, the robot intermittently complained of low voltage. Aloud.)

The main sensor board had light and sound inputs, so we tried those tests next. The light sensor worked a little, but didn’t display a full range of response to bright light, dim light, and darkness. The sound sensors also seemed not as sensitive as expected. Batteries low again, maybe. We were seeing excellent voltage jumps on the board, though, from 0.x to 3.x to 5.x – dark to dim to bright. Was it just that the robot’s display was busted? There was no voltage when we made a loud noise during the sound test. Problems with the sensor board and sound receiver? Mic disconnected? Conclusion: Whatever it was, it wasn’t the chips we replaced after all.

Many other things were kind of working. Sonar was, but it was raining outside so we could only test it for short distances. The pendant seemed to be working. The motion sensor and display were actually working perfectly on second examination. (We had been looking at the wrong board for the motion test. When we found where the right one was tucked away, the motion LED was blinking cheerily.)

The voice synthesizer worked. Tim wanted to do a spoken haiku demo where the robot would spin around afterward, but the drive motors were not working. There were also mechanical problems with the arm as well as electronic ones. Tim is going to strip the arm’s corkscrew motor and other parts down and rebuild them himself. He schooled me in the mechanics of the arm and its claw, but there’s so much to do on this little guy, and we only meet once a month.


So what was wrong with Maai, at base? For one thing, the onboard battery might have needed charged, even though we had it hooked up to wall power the whole time. Some new capacitors couldn’t hurt, either. “They’re 30 years old. When they dry out, they tend to wreak havoc,” said Tim. He may replace the capacitors on the sense board before next time. (Moribund capacitors are a bane to all kinds of retrocomputers, from HERO robots like Maai to Apple IIs.)


We thought of some future improvements:

  • Maai doesn’t have a serial interface, but Tim has the schematics, so we could build one. That would enable saving robot software on an external medium like a thumb drive, and expedite diagnostics, among other tasks.
  • Rare earth magnets to hold the side panels on instead of an elastic belt.
  • Various new masks for the front faceplate area, such as creepy humanoid eyes.

Moral if you want one: Debugging is harder than coding, and repairing something is so much harder than building it from scratch.

See you next Robot Sunday.

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Robot Sunday, Sunday, Sunday


As described in an earlier post, I’m helping my friend Tim Schutz restore his antique Heathkit HERO robot, Maai. It’s like restoring a Mustang, but more interesting and less macho. We meet one Sunday a month.

My Pomeranian Humphrey loafed about while we were working on the robot, but our other Pom, Bridget, had to hide. The robot seemed to fall into her uncanny valley. Odd, because usually Humphrey is more susceptible to that effect, barking at weird cartoons on television. I guess everyone’s valley is different.

Because it had been a while, we decided to run Maai’s diagnostics from the top. The robot mostly passed, although Tim had left the arm at home, so we were less sure about those routines that required it.

We did find the motion sensors weren’t working. And then the vision and audio sensors weren’t either. What the hell? How could so many sensors go out at one time? Was the main sensor board malfunctioning, as we had thought once before?

I stepped through the diagnostic flowcharts in the technical manual, and Tim measured voltages with his meter. It developed there was nothing wrong with the sensors. The hidden problem was that the display board was malfunctioning. The sensors might have been working just fine, but we couldn’t see the results at all. We traced the problem to two chips on the display board, and Tim planned to order them online. Good thing, because all the motion sensor flowcharts had dead-ended in a box reading “Return to Heath Co. for service.”

Dear Mr. Heath,

We are sending you this robot for repair from the future, where it makes the phone in my pocket look like Richard Feynman. Yes, I said the phone in my pocket

Tim’s HERO, Maai HERO


Spent the day running diagnostics on a 34-year-old Heathkit HERO 1 robot with my friend Tim Schutz. (It’s his robot.) At first this activity felt strangely like Raiders of the Lost Ark (“Behold! This primitive robot was built by the ancient Egyptians!”) but, partly because HERO looks a little like R2-D2 (small coincidence), everything morphed into that scene from Star Wars where Luke takes the droids out to his garage for repairs. We were actually punching in machine language routines on a hexadecimal keypad on the little guy’s head. I was expecting HERO to twitch at any minute and start projecting a hologram of Princess Leia. (Tim observed that if it did, Leia would be about 60.) Another difference from the cinematic original was that we were accompanied by two curious, fierce, and slightly alarmed Ewoks, my Pomeranians Humphrey and Bridget.

We determined the robot was in pretty good shape for being so old. The sensor board must be repaired, but the robot came laden with schematics, and in true Heathkit style, everything was labeled clearly. There was even a flowchart in the manual for the necessary fix. The wheel motors work, so the robot can move around, and the arm basically works, but the claw needs a bit of mechanical repair.

I said the robot was primitive, but really it reminded me of a larger version of a 21st-century LEGO Mindstorms robot, and I am filled with admiration for the Heathkit engineers, who made an interface breadboard available even after the head carapace goes back on. Very makery!

Tim named his robot Maai, a Japanese word he knew from Aikido that means “distance”, so its full name would be Maai HERO. Ironically, the distance sonar is the only sensor working right now.

Photo credit: Heathkit catalog circa 1979, via