My first impressions of Scooba were based on not yet having the official Clorox cleaning solution and running with vinegar water. I got my shipment of the Clorox solution yesterday and ran four cleaning cycles on the bathroom floor. New notes:

• I had left both batteries fully charged but off the charger for a week, and Scooba reported one as completely dead and the other didn’t make it through a full cleaning cycle. Looks like I’ll need to keep them on the charger and/or use them more frequently.
• The Clorox solution smells good! (Remember that vinegar is my grounds for comparison . . .) It smells like a cross between some kind of detergent and your widow grandmother’s soap-scented bathroom.
• The Clorox solution seems to clean a little better than the vinegar water — that is, leaves the floor noticeably cleaner. Scooba made visible progress on the dark marks in the faux grout lines on our vinyl floor.
• The Clorox solution puts a shine on the floor! I don’t consider it perfect or done, but the bathroom floor looks way nicer than it did before getting Scooba or after running with vinegar.

Note to other secondhand Scooba owners: Buy the Clorox!

I want to start with a pictorial overview, since I hadn’t seen enough Scooba pictures to understand how different it really is from the Roombas, then proceed to a few comments about my experience with it so far.

Tour Through Scooba

On the surface and from the top, Scooba looks very similar to a Roomba. It’s very slightly larger, but considerably heavier. The handle is used to carry Scooba, but also pushing it down unlatches the tank assembly to lift it out (shown further below).

The rotating brushes on the undercarriage look familiar. But note that the fore squeegee is supposed to keep loose material in the blower/vacuum trough forward of the brushes, and the brushes only scrub and aren’t really meant to pick up material.

The brush assembly slides out the starboard side instead of unclipping directly,

and it folds open to make it easier to clean. Cleaning, by the way, means rinsing under a faucet, not picking all the fluff and lint out by hand.

Scooba moves a lot slower than Roomba because it’s scrubbing the floor, not just passing over and sucking up loose stuff; and its wheels are correspondingly smaller for lower speed. They’re also made of some kind of foam with a diamond tread pattern cut into them, rather than Roomba’s knobby rubber tires. And their suspensions are changed such that the pivot points are inward along the axles rather than inline with the wheels.

Here start the major differences. Roomba’s dust bin is a smallish piece that unclips from the aft end, slides out the back, and dumps out. Scooba’s tank assembly hinges up and leaves Scooba looking like General Grievous’s head (can this possibly be deliberate???) with a lot more interesting things exposed.

The rubber schnozzle on the right is the vacuum tube from the trough on the undercarriage, and next to it is the button to unlatch the brush assembly. The two oblong holes mate with the oblong holes in the brush assembly and similar tubes on the underside of the tank (later) to deliver cleaning solution and remove dirty fluid from the floor.

Below and left of the starboard hole is the socket where the tank’s fluid sensor makes contact. Above and left of the brush eject button is what looks like a spindle to turn a tank pump, although I haven’t completely figured that out yet. The battery is in the center, hiding under the tank when in use, and well away from the liquids splashing about on the floor.

On the left side you can see the blower inlet that leads to the blower/vacuum trough on the undercarriage, with this filter installed.

The filter (upside-down here) slides into the trough and gathers any loose, dry dust (cat fur) floating around inside Scooba. (I haven’t quite figured out yet how that air flows through the tank assembly.) Although everything I’ve had in my filter has been dry, it’s made of metal screen and the easiest way to clean it is rinse it out under running water, a running theme of the Scooba.

Also note that the tip of my filter has been gnawed by the previous owner’s pet (cat or ferret?). This changes its shape enough that it falls right out of the blower tunnel when I pick up the base. When I have some time, I’ll put a dab of RTV on the chewed tip to aid in gripping the tunnel walls.

Removing the tank from the base exposes the tank’s fill and drain caps. Clean solution goes in the right; dirty water comes out the left.

On the underside of the tank, you can see the air path that sucks debris up through the rubber schnozzle on the starboard side and blows air out the trough on the port side, as well as the oblong holes for liquid delivery and pickup, the spindle’s mating part, and the fluid detector plug in the upper left of the lighter blue, opaque part.

Not visible, the tank has internal valves that keep the liquid contained inside it regardless of position — you don’t have to be über-careful moving it from the sink to Scooba and from Scooba to pour out. However, shaking (as when rinsing the dirty tank after use) does open a flapper between the dirty tank and the air path (interesting, wot?), so be prepared.

Back to the base, I found this little gem hidden behind a rubber plug toward the starboard end. I haven’t checked yet whether it’s compatible with Roomba’s serial port. It’s covered by the tank when in operation, so it wouldn’t be practical for connecting to and controlling Scooba as a cleaning ‘bot, but rather only for taking over Scooba as a general-purpose mobile base.

Finally, Scooba’s virtual walls look just like Roomba’s except for color scheme. I assume they’re compatible (except for Scheduler enhancements), but haven’t actually checked yet.

I find it mildly interesting that Scooba’s distance label reads “ 4-7′ ” and Roomba’s reads “ 4′-7′ ”. Who thought that was important enough to make a point of changing it?

Thank you very much, ladies and gentleman, that concludes our tour. You’ll be exiting the cave through our gift shop — please feel free to buy souvenir postcards or have your picture taken with our life-size statues of Roomba, Scooba, and General Grievous. We hope you enjoyed the tour, and enjoy your stay in Branson.

Cleaning Fluid

iRobot contracted with Clorox to develop a special cleaning solution for Scooba, and I don’t have any of it yet. It’s supposed to be a low-foaming, non-slippery solution with a pleasant smell and enough conductivity to register in the tank sensor, and all of these are important factors for proper Scooba operation.

As noted in many places including a comment at a third-party Scooba blog, vinegar makes an adequate substitute for the Clorox solution. No foam, a little slippery, smells fantastic (if you have a fetish for acetic acid, which I don’t, thank you very much), and it registers in the tank. Pour in 2 fluid oz (4T) and fill the rest of the way with water, and you’re (fairly) good to go.

Since mine didn’t come with any Clorox solution and it doesn’t seem to be available in the Wichita area, I’ve been using vinegar (and trying to decide where to pay $5 shipping for a $7 bottle of fluid). Many Scooba owners rave about their shiny clean floors; I would note that this does not happen with the vinegar solution, which leaves my floors fairly dull. Hopefully the special Clorox solution makes them shiny sparkly beautiful.

My Scooba has been halting with bumper (“b”) and wheel (“d”) stuck problems near the edges of the kitchen, and I attribute this to the wheels spinning in the vinegar solution. I’ll find it sitting sideways against a wall in a position Roomba would simply turn away from, and my best guess is that it’s been trying but detected wheel slippage and no motion and decided it was stuck. Hopefully the Clorox solution permits Scooba better traction.

Also, some owners have complained that Scooba is extraordinarily sensitive to having the “correct” amount of cleaning solution (or vinegar) mixed with 1 qt of water — that is, that Scooba refused to recognize that the supply tank was full and ready to use with anything other than the exact recommended ratio of cleaning solution to water.

I had a “Check Tank” message once, and I buffed the tank sensor socket with 2000-grit sandpaper, reinstalled the tank, and started it right up. I think the oxidation on the contacts has a lot more to do with failure to detect adequate tank conductivity than the exact proportions of liquids in the mix.

Leaving Water on the Floor

The very first time I ran Scooba, it didn’t pick up any of the water. This fixya.com post put me on to the idea of putting hot water in the dirty tank and shaking, which got the flapper open. Scooba’s been picking up most of the water ever since.

For the record, it does leave a trail of water behind it on the floor, and I prefer not to walk through a wet room while it’s cleaning. But the parts of the floor that Scooba hasn’t traversed recently are already dry even before the whole room is finished; and except for dimples and low spots, it doesn’t take long at all for the floor to dry afterward.

Leave the fan off while Scooba’s running to give the first pass a chance to stay damp and soften any ground-in dirt, then turn on the ceiling fan or central air afterward and you’ll be just fine.

So How Well Does It Clean?

The iRobot Scooba manual brags about how much dirty water you’re going to pour out of the tank after Scooba cleans, and many Scooba owners positively glow talking about how they love to pour out the dirty water.

Um, in my book, a cleaning robot is not a device to generate dirty water. I can do that with dirt and water. My metric for cleaning robot performance is how clean it leaves my floors. I want to walk in afterward and say, “Wow, that’s clean!”

And on that point I’m mixed. The bathroom floor (vinyl) has dirt in its faux grout lines that’s been really hard to get out by hand; and as I’ve run Scooba in there repeatedly, I can tell the dirt is lightening every time, so it really is cleaning.

But the floors don’t shine, and I’ve been acculturated to believe that shininess is a sign of a clean floor. I’m optimistic that the magical Clorox solution will have magical shining properties heretofore unexperienced with mundane vinegar.

You need to vacuum first. As Scooba has the vacuum trough specifically to pick up loose materials, I find it disappointing that I need to run both Roomba and Scooba. But without prior vacuuming, every possible part of Scooba (blower filter, vacuum schnozzle, brushes, water ports) got clogged with wet or dry cat hair that I couldn’t even see was on my floor.

Finally, I can’t recommend strongly enough having two batteries. Scooba cleans until the supply tank is empty (unlike Roomba, which runs on a timer and/or by discovering the size of your room), which is slightly less than one battery’s worth of charge. That doesn’t mean the floor is now clean (and in fact if it was worth cleaning, it probably isn’t) — it means it has now used up 1 qt of water.

Get a second battery and keep them both charged on the external charger and as soon as Scooba empties the first tank, you can refill it and keep right on cleaning. ¡Muy bueno!

My kitchen floor now feels cleaner underfoot than it has in a long time, even after thorough vacuuming with Roomba, and my bathroom floor is looking better and better. I’m optimistic about the special Clorox cleaning solution doing an even better job and leaving a nice shine; and the bottom line is, not having gone in with unrealistic expectations, I’m very pleased with how Scooba is doing so far.

Yesterday I had time to swap it out and get Roomba working again.

Board Replacement

I had the new board completely mounted and half the connectors wired up when I noticed the first problem:

My Roomba has two dirt detectors, and J9 has two rows of pins, one row to each piezo assembly. The refurbed MB had a single-row J9, apparently from an earlier model with a single dirt detector.

I debated a bit about contacting the seller, but decided it was a waste of his time and mine to ask for a replacement board when I had everything I needed already at hand. I desoldered J9 from my original board (tedious heat-tug-heat-tug-heat-tug that demonstrates how good J9′s plastic is because it didn’t melt and how good the PCB is because the only thing I ruined was one of the test points), and had a much easier time desoldering the single-row J9 from the new board.

Then I got frustrated trying to get the solder out of the through holes. I had some success adding solder to the holes and applying solder wick, but there were three holes I just couldn’t get. Finally I gave up and pulled out the PCB drill bit set — a #68 bit spun gently by hand turns out to be just the ticket for cleaning the solder out of these holes. (Never again will I try to wick solder out of empty holes.)

I cleaned the two-row jack’s leads with a wire brush, soldered it in, took a picture from an angle that looks like I still have the single-row jack in the board, and reassembled Roomba.

Attempt #1

I was delighted to see it turn on when I pressed the power button. I knew that should be what would happen, but it was still gratifying to see it actually happen.

Prematurely. Gratifying.

I took it to the living room to vacuum, hit Clean, and it just burped. It burped when I hit any button. Grrrr.

Diagnostics and Cliff Sensors

The first page I found when searching for why it was “burping” was What is Roomba saying to me?, which says that the “eh” sound means there’s a faulty cliff sensor.

I relocated the Roomba Discovery models’ diagnostic tests page and ran through the individual sensor diagnostics. On test 2, outer cliff sensors, only the starboard-most sensor worked properly; the outer port sensor showed “cliff” all the time. On test 3, both inner sensors showed “cliff” all the time.

Gathering more test materials and retesting, I found that only the outer starboard sensor’s IR LED was lighting my infrared sensor card (apparently no longer sold at Radio Shack, but apparently formerly part number 276-099 and/or 276-1099), and the cliff-sensor IR LEDs were dark. Further, shining the virtual wall’s IR LED beacon into the cliff sensors caused the diagnostic LEDs to flicker, indicating that the cliff-sensor IR detectors (phototransistors or photodiodes) were working properly, so the problem definitely seemed to be in the LEDs.

All three of the dark LEDs individually checked good with the diode tester on my multimeter. Tracing the cliff sensors’ LEDs, I found that the three dark ones were all powered in a single series circuit, fed by the red (anode) and orange (cathode) wires in the top row of J24 at the port end of the main board.

My meter’s diode tester didn’t use a high enough voltage to overcome the forward voltage drop of the series string, so I hooked my bench power supply to a 1KΩ resistor and the series chain. All the LEDs now glowed on my IR sensor card, so the LEDs weren’t faulty (which I had assumed anyway) — the problem was with the driver.

Robot Reviews Forum and Q4 LED Driver

Searching online for advice, I quickly found this forum post titled “Cliff sensor failure apart from one” complaining of exactly the same problem. “Gordon,” a very knowledgeable contributor, indicated that the dark LEDs were all driven by the same transistor, Q4.

I found Q4 on the board and it was twisted, so I straightened it without particularly thinking. (This fact isn’t relevant yet. Just wait.)

Gordon indicated which MB test points correspond to which Q4 pins, provided an apparently reverse-engineered and incredibly helpful schematic of the cliff-sensor LED drive system, and indicated that the Q4 and Q37 bases should have a 1kHz square wave on them, with a corresponding signal on the collectors.

I put the scope on Q4 and its base was oscillating nicely, but its collector stayed high. This made me suspect a faulty Q4, so I quickly and cleanly desoldered it and checked it in my out-of-circuit transistor tester. The tester said it was good with a β of about 220, which wasn’t what I wanted to see. I wanted it to be broken.

And then while I was straightening the leads and pondering what to do next, the emitter leg felt loose and I pulled it out with my fingers. Removed, it looked rather like a dessicated cricket leg you’d find in a corner.

I don’t have SS8050s on hand (that I know of), but they’re all over the MB and appear to be used as general-purpose transistors. I found a 2N3904 with the same pinout in my parts bin (if you think all TO-92 transistors with the same part number have the same pinout, you haven’t shopped enough different manufacturers), tested about the same β, installed it, and the IR LEDs all glowed.

I could have pulled an SS8050 from my original MB, but (1) I wanted to keep it intact, and (2) I wanted to demonstrate that another transistor would work. And so it did!

Sweet, Sweet Success

Roomba powered up again, but this time it didn’t burp (I mean “eh”) when I hit buttons, and it went straight into cleaning mode. Woo-hoo! I took it to the living room and let it clean, and it ran the course and picked up all the cat hair.

Today I emailed the eBay seller just to let him know what had happened. I wasn’t upset and I left him all positive feedback because the board he sold me fixed my problems within my abilities, plus I may have broken Q4 myself while straightening it, plus I had some fun tracing the problem. But I thought he should know what happened so he could check future boards more carefully for customers less fascinated by the process of repair.

He replied:

wow, yes you went above and beyond what I would expect. Thanks for helping out, i’m sorry you had to do so much.

sounds like the glass is half full with you.

There may be some truth to that.

About two and a half years ago, I did something foolish in trusting the wiring instructions from a Roomba battery rebuild supplier and blew up my brand new Roomba Scheduler. Hasn’t worked since, because I wanted to see if I could find the problem and fix it myself before sending it back for factory service. Turns out I can’t (or at least haven’t), but the inside is interesting nevertheless.

Opening

Getting into the Scheduler is easier than getting into the first generation, mainly because it (almost) all comes apart with screws, instead of the (few) latching tabs in the original Roomba. These instructions on fixing the Roomba Discovery “Circle Dance” do a good job of showing the screw locations, although the site then goes on to describe processes specific to cleaning the wheels’ optical sensors that weren’t relevant to my problem.

The most important part that wasn’t obvious to me from the instructions is that the front bumper holds down the front edge of the top, so you must remove the bumper, even if you don’t need to work on the bumper area.

Guts and Wiring

Once the cover is off, the inside looks pretty tidy. As on the original Roomba, there’s one main board sandwiched between the battery compartment and the brush deck, and all the sensors and motors cable up to it.

I had to pull all the cables before I could get the board out, and most of the cables had only one place they’d logically plug back in, but I still took pictures to make sure I’d know how to put it back together again, shown here for the convenience of all the king’s horses and all the king’s men who might be trying this themselves at home.

Having removed all the cables, there’s still an optointerruptor at each end with a bumper lever latched into it. It took some prying to get those loose — port (left when in motion, right when facing it to work on it) side first, then pull the board itself loose of the starboard side.

Main Board

And here’s my main board, with nothing that I can see wrong. No scorched components,

no scorched traces. Foo. (The battery connector is J7 on the solder side, in case you want to trace out from there and try to debug this for me.)

With the component spacing so tight on the board, and no obviously damaged components to investigate first, I didn’t feel like bothering to plug all the connections back in and trace battery voltage while the board was out of its little home. So I gave up (for now, anyway), contacted iRobot to ask about repair, and reassembled the Scheduler.

Reassembly

The most noteworthy thing about reassembly is getting the bumper’s port-end (I think) mounting bosses back into their mating holes. Do those first, then the starboard (I think) end of the bumper, then ease the rest of the port end the rest of the way on. Whichever end it is, do the posts first.

Dirt Sensors

The last thing to mention while we’re in here anyway is the dirt detectors. The second or third generation of Roomba introduced dirt detectors that are supposed to be able to tell when Roomba is actually picking up dirt, so it can spend more time vacuuming that area. I think my dirt typically has a fairly uniform distribution on my floor; but maybe some folks like to send Roomba out to clean up knocked-over flowerpots and whatnot.

Anyway, I’ve always wondered how it could tell when there was dirt — some fancy-schmancy optical sensor pointing at the floor??? — and here’s the answer.

Piezo sensors. Dead simple. Dirt hits them, ting-ting pting tang, and they translate the sound / force into an electrical signal that the Roomba interprets as the influx of dirt. Brilliant!

Next

iRobot promises to respond to a customer inquiry within one business day of receipt, so . . . they’re late. But we’ll see what they say about repair service and cost. I understand they also sometimes have returns and refurbs available for purchase; and at the right price, that could get me a new Scheduler and leave me a spare for parts.

Hm, looks like entire used Schedulers are running ~$100 on eBay, and I just found someone selling the circuit boards for $20 plus shipping. I can’t imagine iRobot touching that price for a factory repair, so it looks like I may be able to do this myself after all. Maybe get a spare Scheduler just for the fun of it, too.

Repairing Roomba Original