Page 1 of 8 12345678 LastLast
Results 1 to 20 of 146

Thread: Kenwood Food Mixer - No Power - Mint Cond - Dead.

  1. #1
    Premium Member

    Join Date
    Jan 2010
    Posts
    1,077
    Thanks
    632
    Thanked 306 Times in 180 Posts
    Rep Power
    300
    Reputation
    4620

    Default Kenwood Food Mixer - No Power - Mint Cond - Dead.

    Hi all,
    Got hold of a mint condition Kenwood Food Mixer KM270. Seems to be very well made. Quite heavy and feels really solid.

    However, it was dead. Moving the Power Slider from 0 to 1 (and others), Nothing. Not a click, nothing!
    I was hoping there would have been an internal 'over heat' fuse or something. But there appears to be no internal fuse
    So my easy thought fix hasn't arisen

    I have checked the power (rear photo), the Red and Blue connections and they read 240v when I move the power slider forward, no clicks, nothing, (they read zero volts when the power slide is on '0'). So moving the power slider to 1 - 10 provides power to the rear board.

    Inside looks immaculate. No burning smells. No components (that I can see), are discoloured, the terminals on the motor look clean. The cooling fan rotates (by hand), with no resistance/clicking.
    Just seems a real shame to throw it away.

    I'm not sure where else to start measuring...









    EDIT: Had to rejoin imgur so that I can 'share' the pics properly...
    Last edited by GT250; 08-02-19 at 09:14 AM.



Look Here ->
  • #2
    Banned

    Join Date
    Jan 2017
    Location
    still above ground level
    Posts
    1,779
    Thanks
    5,562
    Thanked 1,964 Times in 714 Posts
    Rep Power
    0
    Reputation
    35657

    Default

    pull out the brushes normal for them to stick in holders

  • The Following User Says Thank You to hinekadon For This Useful Post:

    GT250 (08-02-19)

  • #3
    Premium Member
    Skepticist's Avatar
    Join Date
    Apr 2009
    Posts
    1,139
    Thanks
    714
    Thanked 670 Times in 525 Posts
    Rep Power
    475
    Reputation
    12780

    Default

    Check the motor winding for continuity - could be a thermal fuse embedded in the winding has blown due to overloading.

    Kenwoods used to be near bulletproof. Got one for a relative nearly 40 years ago and it's never missed a beat.

  • The Following User Says Thank You to Skepticist For This Useful Post:

    GT250 (08-02-19)

  • #4
    Premium Member

    Join Date
    Jan 2010
    Posts
    1,077
    Thanks
    632
    Thanked 306 Times in 180 Posts
    Rep Power
    300
    Reputation
    4620

    Default

    Hinekadon, I have checked the bushes and they are fine, slide up and down easy. Both are firmly on the 'commutator'? Springs are good and aligned ok. Looks to be plenty of life in the bushes.

    Skepticist, Have checked as best I can, from bush to bush, bush to commutator. I think there's a inline fuse going to the bush on the left and that checked out ok.
    Yeah, it looks and feels bullet proof. Just seems a shame to chuck it.

    I put power to the rear board (moving the power slider to position 1), and checked those two IC's, and on all three legs they read 240V - is that correct?


  • #5
    Premium Member

    Join Date
    Jan 2010
    Posts
    1,077
    Thanks
    632
    Thanked 306 Times in 180 Posts
    Rep Power
    300
    Reputation
    4620

    Default

    Quick Update:

    Thar be life!!

    At the front board there is that big IC. On the outside legs they read 240v but then when I was checking the middle leg (0.07xx volts), I accidently touched the left leg (looking at the picture), at the same time as the middle leg, and the motor turned.
    I repeated this very briefly and sure enough, shorting middle to left leg makes the motor and the mixer shaft go around...

    Not sure what to do now. The motor is probably fine. The gearing is fine (no crunchy noises), The rear board might ok, might be something on the front board????

  • #6
    Premium Member
    Skepticist's Avatar
    Join Date
    Apr 2009
    Posts
    1,139
    Thanks
    714
    Thanked 670 Times in 525 Posts
    Rep Power
    475
    Reputation
    12780

    Default

    Assuming you mean the triac (mounted on the heatsink), shorting the left and centre pins is bypassing it and the motor itself does seem OK with the fault being in the triac itself, the gate (right pin) driving circuitry or the power supply.
    The 'transistor' arrowed next to the motor shaft looks like a hall sensor for tacho signal feedback/speed regulation so unlikely to be the root of this problem IE no running.
    See if you can lift the sticker off the top of that 18pin IC to see what it is in order to look for a datasheet online that might have some sample application info. Chances are it's a proprietary chip but you can be lucky sometimes.

    Troubleshooting this thing live is extremely hazardous with mains voltage all over the place so no amount of precautions is too much.

  • The Following User Says Thank You to Skepticist For This Useful Post:

    GT250 (09-02-19)

  • #7
    Banned

    Join Date
    Jan 2017
    Location
    still above ground level
    Posts
    1,779
    Thanks
    5,562
    Thanked 1,964 Times in 714 Posts
    Rep Power
    0
    Reputation
    35657

    Default

    tr 201 could be a diac which is the driver for the triac which is the most likely the fault as they overload if they are stalled and go no go sometimes the smoke get out of them as well .
    if you can find some one with a isolating transformer your safety will be greatly improved cheers

  • The Following User Says Thank You to hinekadon For This Useful Post:

    GT250 (09-02-19)

  • #8
    LSemmens
    lsemmens's Avatar
    Join Date
    Dec 2011
    Location
    Rural South OZ
    Posts
    10,585
    Thanks
    11,867
    Thanked 7,061 Times in 3,338 Posts
    Rep Power
    3153
    Reputation
    132592

    Default

    I have a Kenwood of approx the same age. It was a known problem with them, a relatively cheap fix. I think I paid about $100 to have a service centre fix mine many years ago. That Triac, rings a bell but cannot be any more certain.
    I'm out of my mind, but feel free to leave a message...

  • The Following User Says Thank You to lsemmens For This Useful Post:

    GT250 (09-02-19)

  • #9
    Premium Member
    Skepticist's Avatar
    Join Date
    Apr 2009
    Posts
    1,139
    Thanks
    714
    Thanked 670 Times in 525 Posts
    Rep Power
    475
    Reputation
    12780

    Default

    Jaycar have a triac BT137F which has very similar rating (600V 8A) for under $4 so that would be a quick way to determine if the triac itself is the problem IE not triggering
    There are higher rated devices if you go to Element14 or RS Components but an important feature is that the triac is an 'isolated tab' type otherwise that heatsink will be live
    Last edited by Skepticist; 08-02-19 at 01:37 PM.

  • The Following 2 Users Say Thank You to Skepticist For This Useful Post:

    GT250 (09-02-19),hinekadon (08-02-19)

  • #10
    Premium Member

    Join Date
    Jan 2010
    Posts
    1,077
    Thanks
    632
    Thanked 306 Times in 180 Posts
    Rep Power
    300
    Reputation
    4620

    Default

    Ok.
    Replaced the Triac which was by default isolated (thanks for the warning Skepticist). No good, still nothing.
    I also replaced the TR102 (C9013 - Jaycar replacement 2N222A), which is very close to the Triac. Still nothing.

    NB: TR201 which Hinekdon mentioned on the rear board, is also a C9013. I didn't replace it as it was going to be easier to replace the Triac first and as I saw TR102 was the same as TR201, I thought I might as well replace that, as both are easily got to.

    So maybe I should replace TR201 as suggested by Hinekadon as part of the process of elimination?

    As for the 18pin IC mentioned by Skepticist, I peeled off the sticker and it's a PIC16F716. So looks like a propriety chip
    Interesting thing though (forgive my ignorance), most of the pins are reading 240v: Pin1 is, Pin2 is 2.xx v, but Pin3 and many others are all 240v: Can this be ok, the PDF is sort of saying Max VDD of 5.5V - Is that DC?

    The R104 (next to the Blue spade connection), leading to the middle leg of the Triac is reading 0.4xxVac as the middle leg. The R's around it are reading 240v.
    On Ω's with or without power; the R104 going to the middle leg is 100Ω. And the big R105 (next to the white goo), is only 25Ω (shouldn't it be 108Ω?).

    Any suggestions where to look now people?
    Last edited by GT250; 09-02-19 at 04:28 PM.

  • #11
    Premium Member
    Skepticist's Avatar
    Join Date
    Apr 2009
    Posts
    1,139
    Thanks
    714
    Thanked 670 Times in 525 Posts
    Rep Power
    475
    Reputation
    12780

    Default

    PIC16F716 is a Microchip mcu which will be programmed with proprietary code and no doubt code protected so if that's the problem then it'll be a deadend unless Kenwood will supply a replacement. TR201 looks like part of the speed detection circuit based on the hall sensor and I don't think the problem will be there because the motor is not moving so no tacho pulses produced. TR201 should be easy to test in-circuit with a multimeter.

    What I would be looking for is how the Vcc supply to the PIC chip is produced (3-5V DC) and checking that it is present, then looking to see if the MCLR pin for the PIC is stuck low stopping the chip booting up. Even power up the PIC from an external 5V supply to see if it's alive at all (with no mains supply connected of course).


    The entire circuit can be at or near mains potential because there's no isolation - as long as the PIC has its correct DC supply voltage across the Vdd and Vss pins it doesn't matter if it's floating on top of an AC sinewave. Same applies to all its input and outputs which will be happy provided they're within specs in relation to the Vdd, Vss pins.

    The electrolytic cap near the PIC looks to be part of the PIC power supply, it would be exploded if it ever had 240V AC across it at any time. Looks pristine to me?
    Last edited by Skepticist; 09-02-19 at 06:26 PM.

  • The Following User Says Thank You to Skepticist For This Useful Post:

    GT250 (10-02-19)

  • #12
    Premium Member
    Skepticist's Avatar
    Join Date
    Apr 2009
    Posts
    1,139
    Thanks
    714
    Thanked 670 Times in 525 Posts
    Rep Power
    475
    Reputation
    12780

    Default

    That large resistor (R105?) is 0.1ohm (brown black silver) so there's a definite anomaly there if it measures 25ohm in circuit. Looks like it provides current monitoring when the TRIAC fires but just a guess without seeing the whole circuit layout.

  • The Following User Says Thank You to Skepticist For This Useful Post:

    GT250 (10-02-19)

  • #13
    Premium Member

    Join Date
    Jan 2010
    Posts
    1,077
    Thanks
    632
    Thanked 306 Times in 180 Posts
    Rep Power
    300
    Reputation
    4620

    Default

    Skepticist, I had a look at the PIC and there doesn't appear to be any DC supply to it. When I turned the mixer on (moving slider to position 1), there was no DC voltage to pins 5-VSS and 14-VDD.
    BTW, did you want me to put 5VDC across those pins (with no mains), to 'wake' the chip up? If I connect 5vdc to pin 5 and 14 what would I be measuring (what pin), to see if it's alive?

    In the photo of the underside, the C104 is where pin 5 and 14 are I think.

    I assume the 5VDC or DC voltages come the power slider part. I checked the white connector from that black cable with 240v on and there were no DC voltages.

    I opened up the slider and all that was measurable on those wires was 37V AC on the red wire and a few others - with ONLY the Multimeter Pos probe on red, no Neg probe touching anything?? Am I going to blow myself up here...???

    And a DOH! moment - that R105 was 0.25Ω, not 25Ω!!!






  • #14
    Banned

    Join Date
    Jan 2017
    Location
    still above ground level
    Posts
    1,779
    Thanks
    5,562
    Thanked 1,964 Times in 714 Posts
    Rep Power
    0
    Reputation
    35657

    Default

    seems we got a bit screwed up as theres no mains rectification and no switch mode p/s in this beast then the supply must come from the cap/choke on the bd with the mains going to it and one side is floating according to the current going thru the circuit to produce the "dc" required for the pic and the op amps (c9013) which drives the triac the position sw is only connected to the pic so therefore its only supplies a input to one of the legs of the pic at any one position ( red wire being common )all the rest are speeds set up in the pic and inputs your mistake is not recognising that there is no hard ground or vdd ground as it via a cap to mains ground , therefore you cant measure the dc volts and can only see ac on your meter . a little theory if you put dc on a triac it only conducts for to positive cycle it has to have both cycles to turn on therefore the c9013 is operating as a diac to turn on the triac. going pos and neg with regards to the triacs gate . Isuppose this has some confused and others educated cheers don

  • The Following User Says Thank You to hinekadon For This Useful Post:

    GT250 (10-02-19)

  • #15
    Premium Member
    Skepticist's Avatar
    Join Date
    Apr 2009
    Posts
    1,139
    Thanks
    714
    Thanked 670 Times in 525 Posts
    Rep Power
    475
    Reputation
    12780

    Default

    Looks like a standard setup with a ceramic resonator for the PIC's clock oscillator so powering it from an external 5V source to Vss & Vdd (be very careful to get the polarity correct) , you'll see activity on the outside pins of the resonator with a CRO or logic probe if the PIC is at all functional.

    Do Not do this with the mains connected to the appliance or it could get nasty.

    It seems they're using a novel method of producing that 5V DC supply off the mains that isn't immediately obvious but it can be as simple as a couple of caps, a resistor and a diode (half wave). I'd expect there to be some sort of regulation like a zener or 78L05 or similar too but perhaps the design is just exploiting the wide operating voltage of the PIC (3 - 5.5V) - hard to work out from a couple of pictures.

  • The Following User Says Thank You to Skepticist For This Useful Post:

    GT250 (10-02-19)

  • #16
    Premium Member
    Skepticist's Avatar
    Join Date
    Apr 2009
    Posts
    1,139
    Thanks
    714
    Thanked 670 Times in 525 Posts
    Rep Power
    475
    Reputation
    12780

    Default

    From what I can see in the pics, the 5V power supply appears to come from the PCB with the hall sensor via that 3 pin connector CN102 (red, yellow, green wires)

    Yellow looks like it's Vss and they're using a negative regulator to produce a DC Vss in relation to the mains active.

    NOTE: I'm going by partial pictures so this is guesswork - please trace it out with a continuity tester and no mains connection
    Last edited by Skepticist; 10-02-19 at 11:08 AM.

  • The Following 3 Users Say Thank You to Skepticist For This Useful Post:

    GT250 (10-02-19),hinekadon (10-02-19),Uncle Fester (10-02-19)

  • #17
    Senior Member
    Uncle Fester's Avatar
    Join Date
    Jan 2008
    Location
    Commonly found in a pantry or the bottom of a fridge, searching for grains, fermented or distilled
    Posts
    6,405
    Thanks
    2,289
    Thanked 4,414 Times in 2,517 Posts
    Rep Power
    2046
    Reputation
    81778

    Default

    I have 'circled' the components that are used for the power supply.
    You will need to find the zener diode that is most likely shorted. It could be soldered on the copper side or covered under that white silicon or fixing paste that is next to the black electro-cap, which could also be shorted.

    If no shorts then the big yellow MKS cap could have lost capacitance (hopefully you have cap tester on your multi meter or better a dedicated component tester) and lastly
    if the resistor next to the yellow cap has gone open circuit.


    Last edited by Uncle Fester; 10-02-19 at 12:18 PM.
    Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
    Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
    Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...

  • The Following 3 Users Say Thank You to Uncle Fester For This Useful Post:

    GT250 (10-02-19),hinekadon (10-02-19),Skepticist (10-02-19)

  • #18
    Banned

    Join Date
    Jan 2017
    Location
    still above ground level
    Posts
    1,779
    Thanks
    5,562
    Thanked 1,964 Times in 714 Posts
    Rep Power
    0
    Reputation
    35657

    Default whats

    Quote Originally Posted by nomeat View Post
    I have 'circled' the components that are used for the power supply.
    You will need to find the zener diode that is most likely shorted. It could be soldered on the copper side or covered under that white silicon or fixing paste that is next to the black electro-cap, which could also be shorted.

    If no shorts then the big yellow MKS cap could have lost capacitance (hopefully you have cap tester on your multi meter or better a dedicated component tester) and lastly
    if the resistor next to the yellow cap has gone open circuit.


    whats the component next to the neutral then theres the cap and choke ? or is it a tranx this area is where the
    ';
    '' dc" neutral will be ?? be nice to see the back of this pcb ????

  • #19
    Premium Member
    Skepticist's Avatar
    Join Date
    Apr 2009
    Posts
    1,139
    Thanks
    714
    Thanked 670 Times in 525 Posts
    Rep Power
    475
    Reputation
    12780

    Default

    Just looks like a MOV and noise suppression on that side

  • #20
    Banned

    Join Date
    Jan 2017
    Location
    still above ground level
    Posts
    1,779
    Thanks
    5,562
    Thanked 1,964 Times in 714 Posts
    Rep Power
    0
    Reputation
    35657

    Default yep

    yes thats what i thought but the DC is connected to this part some how thru that cap i reckon dont you ???

  • Page 1 of 8 12345678 LastLast

    Bookmarks

    Posting Permissions

    • You may not post new threads
    • You may not post replies
    • You may not post attachments
    • You may not edit your posts
    •