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Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details. |
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21st Mar 2017, 11:54 pm | #1 |
Hexode
Join Date: Apr 2011
Location: Grove Park, SE London
Posts: 382
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Kenwood Chef A701a motor
Hi guys, I've recently bought a Kenwood chef which I have adored using over the last few months.
Recently, I noticed the dreaded hot electronic smell and a lack of speed control! So I bought a kit of components to repair it. Having removed the motor safely, I replaced the capacitor and two resistors. The speed it fine now. However I can still smell the burning and can see some smoke. Having read up about carbon brushes, I replaced the ones in the Chef and to no avail. I looked inside and I'm sure the culprit is that there is sparking where the brush meets the motor. Also just above the resistor, there is a switch contact which is also sparking! Has anyone come across this?? |
22nd Mar 2017, 12:16 am | #2 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,100
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Re: Kenwood Chef A701a motor
Sparking at the brushes is usually a sign of a burned out segment. This might be more obvious at maximum speed, i.e. that it won't do it. I think replacing the motor is the only hope if that is what it is. Look for a burned mark on the commutator.
I suggest you do what I have done and look out on eBay as people sell broken ones for parts. By far the commonest fault is capacitor failure - and always very spectacular - looking much worse than it is. I got a broken one for £2.50 and now ours is 100% working like new. |
22nd Mar 2017, 9:11 am | #3 |
Retired Dormant Member
Join Date: Dec 2007
Location: Shropshire, UK.
Posts: 3,051
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Re: Kenwood Chef A701a motor
The sparking switch contact is normal for these, provided it isn't excessive. They have an electroemechanical speed governor, which works by pulsing the motor via that switch. Having said that, that's why the capacitor's there, to suppress the arcing. Perhaps my memory's playing tricks, but shouldn't there be two (or even three) caps?
If there's no severe burning of the commutator,you could try cleaning it by wrapping some fine abrasive paper round it and rotating the shaft by hand (non-approved method due to possible embedding of abrasive dust, but it will be OK in practice). If all else fails,drop me a PM,and I might be able to find you a motor. |
22nd Mar 2017, 9:13 am | #4 |
Hexode
Join Date: Oct 2010
Location: Box End, Beds. UK.
Posts: 271
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Re: Kenwood Chef A701a motor
Excess sparking at the commutator usually indicates a damaged armature winding, which is usually fatal for the motor, rewinding such a motor is seldom economically justifiable.
There used to be a chap on the east coast somewhere who sells second hand parts for these things, I have had several parts from him over the years; the infamous little plastic pinion on its shaft, on/off switch and other bits |
22nd Mar 2017, 5:42 pm | #5 |
Rest in Peace
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
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Re: Kenwood Chef A701a motor
A little while ago I was given a Kenwood blender motor, but I can see no markings like you describe. It has a label saying "Part No 23746" and "D5" underneath. If it's what you need I'll happily donate it.
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22nd Mar 2017, 11:53 pm | #6 |
Octode
Join Date: Jul 2011
Location: Staffordshire Moorlands, UK.
Posts: 1,479
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Re: Kenwood Chef A701a motor
ISTR there is a mod somewhere that can be done by adding a triac for switching the motor and so stopping the speed regulator contacts from arcing.
Steve.
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Those who lack imagination cannot imagine what is lacking... |
23rd Mar 2017, 10:36 am | #7 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,100
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Re: Kenwood Chef A701a motor
Since it already has a triac control I would not expect to see sparking at the switch contacts unless the triac is dead.
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23rd Mar 2017, 11:10 am | #8 |
Hexode
Join Date: Apr 2011
Location: Grove Park, SE London
Posts: 382
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Re: Kenwood Chef A701a motor
Wow lots of amazing suggestions guys! I thought with this Chef the triac wasn't present? If it helps the chat, I can send photos? Is there a way to video and post the sparking?? Perhaps that will be useful in diagnostics. I really hope my kenny doesn't have to go on the scrap heap!!
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23rd Mar 2017, 11:50 am | #9 |
Octode
Join Date: Jan 2004
Location: Southport, Merseyside, UK.
Posts: 1,156
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Re: Kenwood Chef A701a motor
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23rd Mar 2017, 3:24 pm | #10 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,554
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Re: Kenwood Chef A701a motor
I would with it unplugged rotate the motor by hand using a wood or plastic tool in the liquidizer drive to make sure it is running free.
Stiff grease will certainly put a lot of load on the motor and it needs to be eliminated. Our original one got a crack in the mincer drive due to frozen food being put through it. It had been re-purposed because an absolutely mint one came up for sale less than 5 miles away. It has still got the dust cover with it. The call was for a new one and this nearly NOS one fulfilled the need. |
23rd Mar 2017, 5:14 pm | #11 |
Retired Dormant Member
Join Date: Dec 2007
Location: Shropshire, UK.
Posts: 3,051
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Re: Kenwood Chef A701a motor
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24th Mar 2017, 9:16 am | #12 |
Hexode
Join Date: Apr 2011
Location: Grove Park, SE London
Posts: 382
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Re: Kenwood Chef A701a motor
Ah the grease is an interesting thought! It gets really hot which I thought originally could be the resistor but physical resistance could also be the cause I suppose. But would it cause all the sparking at the connectors for the carbon brushes? How would I clean the motor? I'm hesitant to dump it all in meths haha.
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24th Mar 2017, 1:26 pm | #13 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,554
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Re: Kenwood Chef A701a motor
You can run the motor for a little while and then see if the motor frame is warm.
Rotating the motor by the liquidizer drive is a lot safer and will give you a feel of how stiff the grease has become in the gear box. |
24th Mar 2017, 1:31 pm | #14 | |
Octode
Join Date: Jul 2011
Location: Staffordshire Moorlands, UK.
Posts: 1,479
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Re: Kenwood Chef A701a motor
Quote:
Steve.
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Those who lack imagination cannot imagine what is lacking... |
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24th Mar 2017, 8:00 pm | #15 |
Hexode
Join Date: Apr 2011
Location: Grove Park, SE London
Posts: 382
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Re: Kenwood Chef A701a motor
Ah the grease in the gearbox- it's not that cos I've re-greased it a while ago. I will take some pictures tonight
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25th Mar 2017, 1:03 am | #16 |
Hexode
Join Date: Apr 2011
Location: Grove Park, SE London
Posts: 382
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Re: Kenwood Chef A701a motor
Ok so here are some photos of the motor with the new components as it is now. some blurry sparking has been captured inside where the carbon brushes meet the motor, and also on a switch contact as you can just about see.
Is the sparking what is causing the motor to get hot to the touch and smell slightly of burning/smoke? |
25th Mar 2017, 9:51 am | #17 |
Dekatron
Join Date: Nov 2003
Location: Near Leeds, West Yorkshire, UK
Posts: 4,609
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Re: Kenwood Chef A701a motor
Sounds like one of the armature windings. Don't let it get too hot and make sure the motor is completely free.
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Mike. |
25th Mar 2017, 12:18 pm | #18 |
Hexode
Join Date: Apr 2011
Location: Grove Park, SE London
Posts: 382
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Re: Kenwood Chef A701a motor
How easy should the motor be to turn? There is some small resistance but not sure if there would be grease inside. Should I just find a new armature winding piece?
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25th Mar 2017, 10:38 pm | #19 |
Rest in Peace
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
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Re: Kenwood Chef A701a motor
What do you mean by 'where the brushes meet the motor'?
The brushes are inside the motor and connect the motor supply to the rotating commutator and hence the armature windings. There is always some sparking between the brushes and commutator but if a winding is faulty, then the sparking is much more severe at one position and the armature can be eroded. If this has occurred, then the motor is scrap. You could measure the resistance between adjacent segments. A good commutator will be chocolate coloured and will not be appreciably worn. It can be cleaned with white spirit. Do not use emery paper or other grit. |
26th Mar 2017, 8:15 am | #20 |
Hexode
Join Date: Apr 2011
Location: Grove Park, SE London
Posts: 382
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Re: Kenwood Chef A701a motor
Ok, I've made this quick video to show you the sparking. Please tell me whether it's an excessive amount. It is on the communicator and one of the switches.
Having looked at a few YouTube videos, it seems my armature winding is stiff! It doesn't move freely. So I was thinking of taking it out and giving it a light oil. How do I get the spindle though off the top? There's a pin holding it in place and it's tough!! https://youtu.be/QQp1e2-iRfQ |