Reply With Quoteman, for $50 i'd use your skills & go and fit a power point @ $120 and you are still way in front.
Kenwood Chef Excel KM210 Speed Control
I have the above mixer and would love some help on this baby.
1) Would anybody be able to u/l a repair manual or suggest where to purchase a copy? Also after some spare parts like rubber feet etc.
2) When turned on, the speed controller does not regulate the speed regardless of the dial setting. It does turn off using the dial though. Is there a common theme with these controllers as the local repair agent quoted approx. $50 to repair it.
3) Are these things difficult to repair? I am an "A" grade sparky with electronics experience and would like to have a go at this myself.
TIA
| Look Here -> |
man, for $50 i'd use your skills & go and fit a power point @ $120 and you are still way in front.
iam a bogan
Lol, not a bad idea mate. But there is something about this mixer being such a challenge, and not to mention brownie points from my wife.
I completely dissasembled and re-assembled the front loader washing machine to have it's drum bearings replaced. Hopefully this one is much easier
With a bit of nouse and a good tool collection, you can probably fix it without a manual. Take photos as you go.Originally Posted by Hakko
I have the above mixer and would love some help on this baby.
1) Would anybody be able to u/l a repair manual or suggest where to purchase a copy? Also after some spare parts like rubber feet etc.
2) When turned on, the speed controller does not regulate the speed regardless of the dial setting. It does turn off using the dial though. Is there a common theme with these controllers as the local repair agent quoted approx. $50 to repair it.
3) Are these things difficult to repair? I am an "A" grade sparky with electronics experience and would like to have a go at this myself.
TIA
Just been fixing my old one. Somehow a couple of pieces of commutator contact came off, broke a brush and stopped.
Spare parts agents listed on Kenwood's web site.
I found a UK site with parts pictures and pricing - which gives an idea of what commonly breaks - triacs and capacitors.
Apparently when the brushes spark, it kills the speed controller triac. Brush price quoted $14 each I think. Armature around $85.
Anyway, I had to spend all that, I figured I would chuck it (well actually it is surplus since we got a new one and I was going to fix it and give it to my sister. We set a $100 repair budget.) So repaired the armature and reattached the wire to the brush. Motor runs at single speed now - just like yours.
I found a website posting that said in was a BT137, which matches the part I saw a pic of on the UK website. BT137 is $4.95 from electronics retailer. Datasheet for BT137 says pin 2 is connected to tab. Still figuring out how to test the triac....
$50 to repair if including brushes and a triac sounds a pretty good deal, but maybe $50 is the quote fee and the parts are extra.
Last edited by blouis79; 14-06-09 at 08:15 PM. Reason: added
Full speed running suggests a shorted triac. Check with ohmmeter between pins 1 & 2. Note that when replacing this part, it is a sensitive gate triac and should be replaced with the same part. Ordinary triacs can give erratic running at low speeds. Also be careful to get a BT137 with the same suffix as the original: -500, -600, -800, which refers to the maximum voltage ratings. It's OK to use higher rating but not lower.
Good post there Biblio
Excellent info, thanks blouis79 & Bibliophile. I'm surprised how hard it was to find some good technical reading on the net. Others have suggested replacing the cap, but I haven't pulled it apart yet.
Wouldn't you get more brownie points from a woman if you bought her a brand spank'n shiny new mixer?
Pulled out the 4.7uF electrolytic cap to test - seems to test OK. Replaced the triac with BT137-800. Now motor not running at all. Triac gate is 240V but can't figure out if it is a dead component in the control circuitry or a dead triac from the brushes sparking again.....
Semiconductors (especially ones controlling mains) rarely go open-circuit. The normal situation (under fault conditions) is for them to go dead short, and in this situation where it is controlling a motor that may have potentially arcing brushes, that's what I would expect to see.
I'd say your triac is actually Ok.
Have you attempted to draw out the circuit?
Drew the circuit this morning. Figured out I had the 4.5uF cap in backwards, though I think it was dead anyway, because I had it in forwards before and it didn;t work either. In any case, having replaced the cap, the circuit has started working again - yahoo!
Needed to see the circuit diagram to be sure which was was the correct polarity for the cap. (Negative towards corner of circuit board. The two pads for the capacitor had double holes with different spacings - Is that some sort of convention to indicate polarity???)
(In my limited experience with appliances, it's usually the electrolytic capacitors or semiconductors that die. In this case I couldn't tell any difference between the functional and non-functional components on testing.)
Set speed to be same as the new Kenwood mixer I have. A metronome was useful for doing this, otherwise I suppose a stopwatch and calculator would have worked.
Speeds: MIN 48 rpm; ONE 68 rpm; MAX 130 rpm.
Other repair tips:
* BT137-800 has live tab connected to pin 2 as original - some similar triac models don't have live tab (though electrically would probably still work since both are connected in the circuit)
* circuit board is covered in circuit lacquer which should be replaced to prevent carbon deposits from the brushes causing shorts
* gap between motor magnet and circuit induction posts is around 0.5-1mm - fine tune to achieve correct speed using the two sprung screws.
* belt tension is set by the motor position in its mounts - plastic parts have cams to permit adjustment. My belt seemed marginally bigger than that so just used finger tension to pull the motor housing towards the side of the casing.
Considering I have patched broken armature contacts, mended a few broken armature wires, and rejoined a brush wire with circuit conductive pen, I am a happy boy this machine is working. Parts cost BT137 $2.50; 4.7uF capcitor $0.50.
Thanks all for the clues.
Last edited by blouis79; 21-06-09 at 10:58 AM. Reason: fixed price
weirdo (21-06-09)
Great that you sorted it. Post the circuit here if you can for the benefit of others who may need to repair one of these things
Kenwood manuals apparently were available online from kenwoodservice.co.uk at one stage, but not now.
Disassembly order to remove motor (from memory and hopefully omitting unnecessary steps I used):
1. remove 3 loose covers over top of body; front cover for mincer drive held on by spring lever
2. remove spring lever plastic cover and lower body cover (2 screws)
3. remove blender mount (three screws, note orientation of blender mount), top cover, drive belt
4. underneath, remove mains cable termination cover, and disconnect mains lead
5. raise mixer top and remove slide/strut mount from top housing (2 screws)
6. remove speed control knob - cover has 2 clips (one each end) - lever with fine blade; remove small spring clip
6. remove mains termination strip and motor cover (should unhook at hinge end)
7. remove motor (three screws at top)
At this point, hopefully the motor and circuit will come out.
I also removed the hinge pin (retained by one E clip at front) and body raising spring, which separated the top and bottom housings and made it easy to get the motor out without removing the knob.
Note the position of the 2 sprung screws and the gap between motor shaft magnet and the 2 inductor pins on the circuit board.
To remove the circuit board, undo the two sprung screws, lift microswitch off its locating pins, and slide the overload switch from its mount.
Remove the two screws holding the circuit board cover on the circuit board.
It may be possible to remove the circuit board for repair without removing the motor, but this would be easier when the top and bottom housing are disconnected. But you need to motor out to replace brushes.
I found a web site listing generic brushes for much less money than the genuine ones. If my machine needs new brushes in future, I will see if I can get some generics from a motor rewinder. (May need to reuse springs and brush termination washer.)
I found the two mains wire connections to the circuit board were partially fractured (from flexing). So these should be checked and repaired if necessary - perhaps with more flexible cable for the keen.
The best part I found was that the motor/speed control assembly can be connected to power and bench tested, as long as the motor is prevented from rolling onto the floor (which it did to me when the speed control was dead).
All I have at present is hand-written half-scribbled drawing, and have only identified the capacitors. I was going to put it in a circuit simulator/design program but have no immediate need. See post #16.Great that you sorted it. Post the circuit here if you can for the benefit of others who may need to repair one of these things
Last edited by blouis79; 21-06-09 at 04:00 PM. Reason: changed PM to see post below
Well done blouis79 on fixing your problem. The extra holes you mentioned are to accomodate different sized capacitors. Probably at some time during their production run they had alternate suppliers. Electrolytic capacitors are difficult to test as they have several failure modes. They can go short circuit, lose capacitance or develop high series resistance. A multimeter will reveal the first problem, a capacitance meter will diagnose the second but only an ESR meter will show the third which in recent times appears to be the predominant failure mode. There used to be a kit available from Jaycar to build your own but, unfortunately, it seems to have been discontinued.
So, Hakko, how are you going with yours?
I guess it's unlikely I will do much more with this circuit.
I was contemplating using it to build a power tool speed control, since the published kits all appear to have problems. The Kenwood circuit appears dependent on the moving magnet providing feedback to the inductor circuit - presumably an electronic version of the old mechanical governor they used to use. I presume therefore it will not be so much use to me for other purposes.
So I will post what I have....(should have taken a photo of the other side of the PCB *&*^%$^)
PCB:
Messy circuit diagram (not all components specified):
Last edited by blouis79; 21-06-09 at 04:08 PM. Reason: clarification
All the time I spent trying to debug the circuit would have been better off just swapping out components. If I'd just replaced the triac and large electrolytic capacitor, would have saved a few hours fiddling about.
(also should have taken photos of the repaired bits but at the time was happy to just reassemble the motor and see if it worked)
Found a description of an ESR meter...looks cool.
FWIW, I extended the broken armature wires with small bits of wire pinched from cat 5 cable - was a little larger than original but small enough to work since I didn't have any other scrap wire small/large enough; wound short coils on the ends; used the coiled end(s) to crimp to the broken wire, then soldered the connections; lacquered over.
(Since then I found some posts here on motor rewinding suggesting it could cost hundreds of dollars, so the new armature for $85+ is probably a reasonable thing if one could justify fixing the old motor vs throwing out the whole machine.)
Last edited by blouis79; 21-06-09 at 04:37 PM. Reason: added another link
The capacitor ESR meter I was referring to is a a local invention by Bob Parker.
He was published in Electronics Australia and Silicon Chip magazines.
He also has some other projects which may be of interest to people trying to service electronic equipment like the Line Output / Flyback transformer tester which is also useful for testing switch mode power supply transformers and other inductive components (Aug '98)
But you've learned something and saved some money. How good is that?All the time I spent trying to debug the circuit would have been better off just swapping out components. If I'd just replaced the triac and large electrolytic capacitor, would have saved a few hours fiddling about.
I finally got off my arse and repaired the Kenwood Chef. I followed everyone's advice and replaced the 4.7 uF electro (with an RB type mind you) and the triac with a BT137-600.
I checked the state of the brushes, and had plenty of meat. There was minimal carbon build-up around the motor. An ebay seller had the brushes for $25.00 with free P&H. The local repair shop wanted $26.00 for the pair, but wouldn't give me a trade discount......oh well, I'll replace them later.
I put everything back together, carefully lining up the inductor pins so they were parallel, and eyed a "good" gap of 0.5 - 1mm or so.
This baby worked beautifully first go, with a good ramp up. There is nothing better than getting the satisfaction of fixing something yourself!
Many thanks to all who posted and offered their input. It's very much appreciated
Last edited by Hakko; 17-10-09 at 06:25 PM. Reason: spellink
Posting Permissions
Bookmarks