Please clean brushes......Any hope for my new (to me) friend

[karride]

I've always wanted a Roomba, but could never really justify spending such a large amount of money when my old walmart special vac still works just fine. So I was overjoyed the other night when I stumbled across a 500 series in a local thrift store for $35.

Even better when I got it home, after giving the brushes a good cleaning, it started right up! the battery was weak, so I have been running it until it dies and then letting it charge overnight. After two nights of this, I had gotten from about 15 minutes of run time to 60-70 minutes.

Anyway, last night I set it in our bedroom and let it go for another full drain. It hit a couple of surprises under the bed and needed rescuing a couple of times, but was humming along smoothly for the most part. Then suddenly it stopped and wanted it brushes cleaned. I cleaned them and sent it on its way, and a short time later gave the same message.

You can guess where this is going. It thinks its brushes are jammed. fortunately when this happened I found this site, and have since cleaned the yellow end bearings, and opened up the gearbox and cleaned all the crud out of there (didn't have white grease, so I have not yet re-lubed, will try that tonight), and also checked to make sure the little motor hold up wire was still attached. The motor will spin both directions with a 9v battery, and I also put it in manual diagnostic mode and the brush test will spin the brushes backwards for a second, then run them forward until I stop it. But if I put it on a floor (carpet or hardwood), the motor acts like the brushes are jammed, and runs the motor forward a little, then reverses

Anything else I can try? I read on there the try running it with out one or both of the brushes, which I will try tonight.

[vic7767]

The clean brushes error is triggered by the amount of current the brush motor consumes. If the brush deck is running without lubrication then that may be the cause.

[karride]

Thanks. there is a little lube still in there but its pretty nasty and contaminated, so I'll thoroughly clean the gearbox, hit it with fresh lithium, and cross my fingers tonight.

[karride]

Tonight I thoroughly cleaned and lubed the gearbox, still no love. I even tried running it with no brushes.

So I tore it down to the PCB and found this IC that looks like it has burned. Location is U1 on the board, Marking are the TI logo first line of numbers is 7BJ5L3KG4, second line is HC02.

Can anyone confirm that this could be the cause of my issue? I'd hate to buy a ne PCB and this not be the problem.

I'm going to try and get a hold of a variable power supply so that I can measure the motor current draw.

[vic7767]

I would suspect the CHM and its brush deck are the real issue. It may be warped or the gears very worn or the brush motor may have a marginal winding.

[TechGuy]

Don't fool around with the motherboard. It is the CHM problem.

Take all the gears out of the CHM. Run your Roomba without the brushes. Is there any more clean brushes messages?

[mfortuna]

It is hard to tell if there is anything wrong with U1. It could just be residue from the manufacturing process.

[karride]

So I guess everyone agrees that its the motherboard then, right?

Thanks guys, mfortuna is right, I took a fingernail to that spot and it came right off, so not a visible board problem. I'll order a new CHM.

Much as I'd like to I can't really justify buying one of vic's rebuilt heads until I see my Goodwill purchase work reliably. So if I'm buying a stock CHM, would I be better to just get a 500 series head, or is it worth waiting on the 700 head to come back in stock?

[vic7767]

If you get the 700 CHM and add an Aerovac dust bin it will help extend the CHM operational life since less debris will work its way into the brush gears.

[karride]

Reading some reviews about iRobot and how long stuff takes to get back in stock, I think I'll go for the 500 series head for now, then once its proven itself I'll buy an aerovac and one of your sealed bearing heads.

EDIT: For anyone like me that is looking while iRobot is out of stock, there is a seller on NewEgg selling the 700 series CHM, see: http://www.newegg.com/Product/Product.a ... 0YP0F58758

[karride]

Well, got my nice new CHM this afternoon, reassembled my little friend, started him up......and *KaThunk! KaThunk! KaThunk!* Same problem

So I guess that leaves the board?

[vic7767]

The noise from the CHM is the Roomba detecting an overcurrent condition that is normally caused by something tangled within the brushes and the program attempts to untangle the brushes by momentarily reversing the brush motor. Try running the new CHM with the two brushes removed and see if the CHM still makes the untangle noise.

[karride]

Yes, it still makes the noise, even with the brushes removed from the CHM.

[TechGuy]

This is a tough one! But I don't think that the motherboard is the problem. Run your Roomba without the CHM. Is the noise still there?

[vic7767]

I'm starting to suspect a poor alignment issue between the CH Module and the Roomba frame that it mounts into.

[karride]

Well, I don't think its going to make the sound since the brush motor will not be in place to reverse I tried running it without the CHM, but its too light without it. I guess I can take my old CHM and pull the connector down so it can be installed without actually being connected, but that will have to wait until tomorrow night.

[karride]

I'm starting to suspect a poor alignment issue between the CH Module and the Roomba frame that it mounts into.

How would one determine this is the case? It doesn't seem like it takes a lot of effort to install the CHM. Its not binding in one place more than another (that I can feel anyway).

Anybody want to swap Roomba brains with me to find out for sure?

[vic7767]

How would one determine this is the case?

When the CHM is dropped into place do all four mounting screw locations seat flush with no space between the CHM and the Roomba frame ?

Also, what model number is your Roomba ?

[karride]

Serial number starts wit KYN5500....so that would be a 550 then yes? number from the bottom of the Roomba has worn off.

I'll check fit tonight, and I'll mod my old CHM so that the brush motor is not connected, and see if it still dies.

[karride]

I ran it tonight without the CHM motor powered up, and it ran fine (well, other than the brushes not spinning of course). Not quite sure if that tells us anything, but there it is.

I checked the fit of the new CHM, and don't really see any problems, it drops in with no binding and the screwtabs are flush with the body. I tried leaving the screws about 1/4 turn loose, just thinking that maybe that would give it some wiggle room, but still no dice.