CT Mini quit

[Michael Kellough]

My first generation Mini suddenly stopped.
No weird sound, smell, or any other sign that something was about to fail.

I’ve run this thing a lot.

Does this problem resemble worn down brushes and can they be replaced?

 

[AlexThePalex]

It could be the brushes, but it could also be something else.

I've had this happen twice with my 2006 Mini, and both times it was a wire break inside the power cable. So that's the first thing I would check. If that's not it, it could be the brushes, which can be replaced.

But it could also be the motor or the electronics board. You can't be sure about it without a thorough inspection.

Every part of the Mini can be ordered and replaced to get it working again.

 

[Michael Kellough]

Thanks Alex. Gotta clear a bench and disassemble.

 

[Michael Kellough]

Finally took time to look into the motor.

Checked continuity of power to everywhere that should have it when in operation and it was all good so figured it was the brushes for sure. Removed one brush and it looked fine but since I don’t know how long it should be... Removed the other and saw that the carbon rod incorporates a clever non conducting stud that stops the flow of power when the brush is too worn.

Called Festool to get replacement and (at this point, it’s an old model) they only sell the complete motor for $130+.

Found places that sell similar looking brushes for the Domel motors so I’ll try that.

The original brush has no identification except HG 26 embossed in the carbon.

Haven’t found that but have ordered a pair of HG 25. Maybe...

 

[AlexThePalex]

Well, that's bad that you might have to ditch the entire vac just because of the brushes. Hope you still find the right ones.

In the UK there are a couple of spare parts websites that tend to carry parts for older tools also, but I am not sure how much use they would be to you for your 110v motor. 

 

[Michael Kellough]

There are lots of brushes out there in the world and it’s such a simple component that I’m pretty sure I can get something to work and salvage the vac.

I was really impressed by the little built in cutout thing in the brush. It’s a little plastic rod backed by a spring embedded in the back end of the carbon brush. When the carbon wears down (and spreads carbon dust all over the inside of the vac) and there is too little of the brittle carbon to contain the little rod’s spring, it launches the rod forward pushing the brush off the commutator instantly stopping the flow of power to the motor. That’s why I didn’t hear the rough or intermittent sound I’ve heard before when the brushes wear out.

I’ve never had a 220v universal motor so no idea if those brushes differ from 110v versions. Maybe 220v brushes are smaller?

 

[AlexThePalex]

Yes, it is certainly an ingenious design with that little spring inside. Festool says they do it like that to protect the commutor from damage from the brushes' end part.

I don't know if 220v brushes are different from 110v. But I do know that there are many types of brushes and they can be different in hardness and electrical conductivity. I know from experience that you can not just put any brush in any tool. I have tried to improvise a couple of times with off-brand brushes but it never worked.

 

[Michael Kellough]

Didn’t know there was much difference in brush composition.
Guess I’ll have to keep my fingers crossed.

 

[Michael Kellough]

Another disappointment on opening up my Mini was to discover that the fairly new genuine Festool fleece bag had dust all over the outside. The bag wasn’t torn, the rubber collar was loose. Half was attached to the bag and half flopping loose. And no, I didn’t crash the pipe into the thing, it just wasn’t made right.

Another gripe. I use a Dust Deputy with my Mini almost all the time. Recently I upgraded from a non-AS  hose from DD to Mini to an AS hose Oneida sells. It fits on the DD easily, it’s made of a soft grippy plastic, but the fit into the Mini is only made by cramming and twisting. It can be done though.

My complaint here is that the interior of the hose is the opposite of smooth. A fairly deep spiral rib catches a LOT of dust as I discovered when I pulled it out of the Mini. Experience has taught me to always have the vac running when I disconnect a hose but since the brush stopped the machine I didn’t get the chance.

 

[Michael Kellough]

Hopefully, we’ll see when the parts get here.

[member=10147]jobsworth[/member]  not all “the old timers have left the site”.

Another myth is that Festool doesn’t monitor the site.

Just got a phone call from the Robert, the director of customer relations at Festool USA.
Christian O. (needs no introduction for old timers) was checking the site and found out about this old timer’s problem and contacted Robert.
Turns out, like Alex said, the brushes are still available and Festool will send a pair.

Robert said that when I called Festool to order brushes I didn’t receive all the information I should have.
The brushes aren’t readily offered because when the brushes run all the way down (typically at about 800 hours use) the motor bearings are failing or likely will soon and for the sake of productivity the motor should be replaced.
The customer is supposed to be informed and then offered the choice of buying new brushes or a complete new motor.
I don’t depend on this tool to make a living so I’ll take a chance on just replacing the brushes.

Also, they’re sending replacement bags.  [thumbs up]

Glad to get the parts, and to know I haven’t yet exceeded my gripe allotment.

 

[AlexThePalex]

Ha, that's quite a favourable turn of events.  [big grin]

Christian O. is one of the biggest Festool bosses right now, nice to see he personally took it on him to help you. Guess he's also reminiscent of those good old times, sometimes.

And good you can get the brushes.

 

[Michael Kellough]

Posted too soon [tongue]

The package arrived this morning.
A nice strong box holding a little envelope containing brushes and a box of fleece bags.
The box was neatly stuffed with bubble wrap as if something delicate was inside.

Unfortunately the brushes are for a CT 26/36 (according to the label on the envelope) and I need brushes for a first gen CT Mini.

The new brushes do say HG 26 on the carbon but the cartridge is very different. This one does not have an integral spring to drive the carbon forward. The spring must be a part of the motor in the CT26/36 vacs.

[attachimg=1][attachimg=2]

 

[Michael Kellough]

The brushes I found on eBay arrived in the mail.

[attachimg=1]

They’re almost identical to the originals. All dimensions the same except length, 2mm longer.

[attachimg=2]

Looks like if the brush is backed out the back the brass case could be cut down.

[attachimg=3]

Before cutting I checked how close the original brush case got to the commutator.

[attachimg=4]

Realized if the little clip that prevents the case from being pushed away from the commutator was cut 2mm shorter the new brush case would fit the same as the old, it would just stick out 2mm farther and the vac case could accommodate that small difference. The little score in the brass (I added) shows where to cut.

[attachimg=5]

The new case on the left, old on the right.

Put it all back together. As far as I can tell, it runs well.

 

[AlexThePalex]

Good to hear that worked out. Would have been a shame to trash it just over a couple of brushes.  [thumbs up]

 

[flair woodworks]

Hi Michael,

I am quite sure that the CT26/36 do have a separate spring advancement mechanism. It looks kind of like a clothes peg spring, only the legs are about 3” long.

However, I’d like to take this opportunity to point out that some brushes do have built in springs and an integral retaining clip that keeps the brush from advancing until the clip is lifted after installation. This makes installation easier.

And I’m going to make a note to get a pair of spare brushes for my CT 26.