CT22E variable speed not working (fixed)

[i814u2]

UPDATE: fixed. see below.

First post, and of course I lead off with an issue.

Hello everyone. I've got a CT22E where the variable speed does not work. I'm fairly certain this is out of warranty (I would guess it was purchased around 2008), and I have no paperwork for it.

That being said, I opened the unit up and did some investigating. The only other thread about this issue, that I was easily able to find, had a post mentioning a broken post form the knob to the rheostat. That is not the case here. I also de-soldered the rheostat and tested it, without issue. It shows roughly 0 ohms (with the accuracy of my meter) at the "max" speed setting, and roughly 261K at the "min" speed setting (the device has 250K stamped on it, so I'm guessing within the spec for this part).

That being said, the vac runs just fine otherwise. However, no speed control obviously hampers my sanding ability.

I just picked up a couple of used sanders (RO 125, DX93E), on Craigslist. I know the variable speed used to work, but I haven't had the sanders and haven't used the lower speed. So I'm not sure what died or changed.

Any thoughts? Any ideas on cost to fix? Nothing is physically noticeable on the main board, but I haven't tested any of that yet. I'll search around for a number to call and ask, but I just wanted to see if there were any ideas out there.

Thanks, I'm excited to get up and running with these sanders.

-Josh

UPDATE: see my post about the fix, below.

 

[AlexThePalex]

If it's not the rheostat or the knob then it's some other part on the electronics board. You can get the replacement electronics board as a whole from Festool, but this is expensive to replace, $141.

You can check all available Festool spare parts and diagrams at their EKAT catalogue.

I'd check to see if I can find another faulty part on the electronics board and replace it myself. Perhaps it's only a faulty capacitor somewhere. Otherwise the only solution is to replace the entire unit.

 

[i814u2]

Thanks for the response. I called Festool over lunch and came to the same conclusion.

I'll test some more components first and then either find a used CT, or bite the bullet and buy a new board.

I'll post back with whatever I end up doing/fixing.

EDIT: I wanted to also say "kudos" to the folks at Festool. This was the first time I had called and I was speaking with someone within less than half a minute. There was one set of automated questions about what department I wanted. Parts and Service was #2 on the list. That may seem like there are many issues needing parts and services but I'd say it's simply smart thinking. How many people call for service vs calling for something else? Anyway, I pressed "2" and a man named Chris answered within 5 seconds at the most. I explained why I was calling and he transferred me to Dave. I mentioned my issue, he said that was odd and would have expected a broken/stuck knob or bad rheostat but since I had tested them his next thought was the main board. He mentioned that since I was testing items, I could potentially test the transistor next, since that was essentially the next big component in the line. He basically stated to test a few things and then get the replacement if needed.

That kind of service, to me, is amazing. Normally when you call a company and state that you've been testing things yourself, they are prompt to remind you that they don't cover your work, etc. These guys answered my questions directly, gave me a part number and a price, and some free advice.  Once again, the service is definitely part of the price of the product. If nothing else, it's definitely a value added to these products (let me rationalize the cost how I want, ok?).

 

[i814u2]

Quite the late bump on this thread. Since this wasn't my only vacuum, this project had been put on the back-burner. However, I had a break-through and I'm updating because I finally solved my issue.

Anyway, on to the fix: after some searching, learning, testing, much more learning, more testing, I narrowed the most-likely culprit down to a single chip on the main board. Since this chip was only a few dollars and my level of understanding/testing of ICs is still limited, I just ordered the chip to see if it would work. Turns out it was the issue and now everything works fine.

More details: The chip in question is a U211B3. It is a speed control chip that basically runs the speed of the whole device. When it failed, the vacuum simply stayed on high speed all the time (better than not working, at least). I purchased the replacement chip from a china-based seller on eBay. It was $2 plus $4 dollars for shipping.
The attached photo shows the underside of the board, with the chip pointed out. Please ignore the through-hole resistors. Those are originally surface-mounted resistors, but I lost one and damaged another during one of my learning phases, early on in the process.

I replaced that chip (not terribly fun to remove. use patience, research IC desoldering if you don't know how, practice on a junk board if you can, etc.), did some tests before re-assembling, and now all is well.

This may be well beyond the desired hassle-level for most wood-workers. But, if you're like me, you may find it a useful skill/project to tackle. I now have my vacuum working again for less than $10, plus time invested.

Also, I'm fine bumping my own thread, but rather than bump another thread from 2010, I thought I would link it here:
http://festoolownersgroup.com/festool-tool-problems/ct22-variable-speed/
That appears to be the same issue I was having, but I have no way of knowing if the solution would be the same (or if the suggestion in that thread was helpful for the OP).
I'm merely linking it here in case it helps anyone when they search.