Kenwood chef A901 rough at low speed

powdies

I was given a KC A901 which has become a labour of love :-). I first replaced the blown capacitors and 56 ohm 2w resistor, it wasn't operating across the speed range correctly so I have adjusted it on the speed screws and now that is ok. But it is very rough and erratic at lowest speed (about 60 rpm) - the actual movement of the planetary action hub looks ok ,but it's making a very unneven noise at anything up to about speed 3. My apologies if this just sounds daft but instead of making a regular voom.. voom.. voom.. voom motor rotation noise it is making an irregular voom.. voo-voom.. voo-voo-voom.. voom.. voo-voom sort of staggering noise, a bit like a car engine misfiring. The higher the operation speed the better it sounds. Last night I checked the carbon brushes, which have plenty of carbon left. Help! I'm out of ideas and I'm hoping someone can suggest something or tell me if this is what it should sound like at low speed (surely not?). Many thanks for any help you can give.

keeweechris

Hi powdies, I'm trying to repair an older A701 with EXACTLY the same symptoms! Did you work out what is wrong with yours?

The A701 is probably different electronics, as it doesn't have a triac, but I think it works on similar principles (the centrifugal govenor). Nothing looks obviously burnt, but I'll start replacing the caps I think. I checked the brushes, cleaned the comutator, and cleaned the speed switch contacts. It still sounds like a Harley engine at low speeds.

Thanks for any help

Barneysmom

Is it an old machine that has been well-loved?
It could be that the shaft is worn and has excess play on it.

If you can't change the bearings, which is probably the problem then try adjusting the fan distance by loosening the screw then push the fan in toward the motor and retighten the screw. Then adjust the speed screw afterwards.

keeweechris

Thanks Barneysmom, but its def the motor acting erratically, not the bearings. I've cleaned/greased the bearings and theres a good amount of longitudinal movement in the shaft, and the rotor spins very nicely.

But yes, it's a very old (1960's I think) machine that has beaten a lot of cakes in its life! And a lot of cake has ended up inside the machine!

I've got the motor out and running on my desk, and you can see the speed controller switch sparking erratically as it speeds up and slows down, while I keep the speed knob in the same position.

Badrick

If you Google "Kenwood Chef (model number) Repair Kit, you can buy kit to repair speed controller. Kit comes with instructions, but you need to be able to solder as it involves changing resistors and capacitors.

kefir

Hi,

I have a Kenwood Chef A901 with the exact same problem, it runs very unevenly at low speeds, and even occasionally virtually stops between the erratic pulls of the motor when running at the very lowest speeds. I'm busy disassembling my machine, but I'm struggling to remove the brown flat cover at the front of the top section, where the logo is. I read in another thread on the site[1] that I should be able to remove the top panel after I remove the lower panel, but my lower panel's already off, and the top panel is loose, but it's stuck to the front brown panel.

Do any of you have any tips on how to remove that? A pointer to a disassembly manual? I'm trying to pull it right off, because I don't see how else it's attached, but I'm afraid I'll break it, because it's not budging. If I get that off, I'll get more access inside and can try to find out more.

[1] hxxp://forums.moneysavingexpert.com/showpost.php?p=5181087&postcount=19

change to http, I'm not allowed to post links as a new user.

kefir

Duh, I didn't realize the red release lever was there to release the brown front panel, I thought it was to release the tools... When I figured that out, I managed to disassemble everything easily. Now all I need to do is find out what's causing the erratic motor movement.

kefir

Is this what your machines sound like? The second video illustrates (briefly) how the machine runs smoother at higher speeds.

hxxp://youtu.be/-i6uOxl6Vdw
hxxp://youtu.be/QDeEtC660h4

Replace hxxp with http. I'm still not allowed to post links.

kefir

On further inspection, and with a few tips, I have discovered that the shaft in my motor isn't attached as well as it should be. The shaft moves ever so slightly up and down in the motor, and apparently this could be the cause of the glitches.

I think I know how to fix this as well. At the bottom of the motor there's a screw that holds the bottom fan to the shaft. You'll need a 2.5mm hex key for this. Unscrew it a little bit, squeeze everything well together to avoid any possible slipping, and then tighten it well again. Now reassemble and test your machine.

I'm afraid I didn't understand how everything hung together at first, so I actually unscrewed the four nuts and bolts holding the whole motor together. Because of that, the motor came apart as I undid the screw at the bottom of the shaft. Next I tried to reassemble the motor, unfortunately without first removing the electrodes from the sides of the motor (the white diamond shaped things where the wires are attached). Because of that, I've broken off both of the electrodes, which really sucks. That's what I get for trying to ram it back together again as soon as it came apart, without understanding how it worked. Guess it's time to buy a new motor... I thought I'd share in case this is of use to anyone else.

sketchy19

Any progress on this?

My mum has given me her old A901. I have given it a full service. It has had new capasitors, resistors and triac. I have striped it down and cleaned the comutator, all the winding seam ok, there is no play in the shaft vertical or horizontal and it turns nice and smoothly. The brushes are in good condition and i have cleaned the contacts on the speed govenor. Despite all of this it is running lumpy at low speed and i cannot understand why.

From what i can see the speed is controled by the plate attached to the fan lowering onto the white nylon button as the speed increases this pushes the nylon button down opens a contact so the motor slows the contact is made motor speeds up and so on. Is that about right.

There is some arcing on the speed govenor contacts is this normal?

The lumpy running feels like the kick you get as the power is re-introduced.

I think it may be the mechanical side of the govenor that is causing the lumpy running but it is so basic i cannot see why.

I really hope you can help as i am all out of ideas.

Any help or advice would be much appreciated.

kefir

Hi,

I managed to buy new graphite brushes on ebay, and fixed my motor. It was really no sweat. However, I have yet to fix the uneven speeds, though I haven't really worked on it much lately. But another guy on the WACEM mailing list managed to fix his Kenwood Chef A701 motor, which had the exact same problem. Unfortunately he did several things, and wasn't sure exactly which fix solved the problem, but here's what he did:

hxxp://groups.yahoo.com/group/WACEM/message/26277

Good luck.