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Trying to fix Dyson DC24

Discussion in 'Repairing Electronics' started by Corrie, Oct 18, 2015.

  1. Corrie

    Corrie New Member

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    Very new to electronics, learning as i go here;

    Anyway, the brush motor wasn't spinning,. so i strip the Dyson down seems to be getting power to this little circuit board but not to the motor connected to it.

    [​IMG]

    100uF 400v capacitor, GBU807 (Bridge Rectifier) and a resistor (WP4S 1R0 5%), there are some on board resistors on the back too. With my multimeter i tested everything i could, found the resistor was blown, removed from circuit and sure enough no connection was getting through it.

    Found what i thought was a replacement one from here:
    http://cpc.farnell.com/welwyn/wp4s-1rja2/resistor-1r-4-watt-5/dp/RE06394
    Soldered it in and built the Dyson back together; Turned it on and was rewarded with a lightning show as electrical arks jumped all over the little circuit board, luckily the dodgy switch on the Dyson turned the thing off almost right away and the components seem to be testing ok.

    I just want to know what i did wrong, two theory so far are 1, Wrong resistor. or 2, Motor shorting out. I can test the motor resistance, but not sure what i should be getting from a 240v DC motor. Anyway, could do with some constructive advice here.

    thanks
     
  2. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Do all 4 diodes of the bridge rectifier check out ok?
    What is that skewed lump of something top right?
    What is that little 'pocket' thing next to the bridge?
    The cap seems to have blown a hole in its side.
     
  3. Corrie

    Corrie New Member

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    Do all 4 diodes of the bridge rectifier check out ok? -Yes.
    What is that skewed lump of something top right? -pad to protect cap.
    What is that little 'pocket' thing next to the bridge? -silicon (thermal?) gell.
    The cap seems to have blown a hole in its side. -Just the picture, it looks fine and test ok.
     
  4. dave

    Dave New Member

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  5. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Looks like there is varistor next to the brrdge with a chunk out of it.

    the disk looking thing.

    What is the silk screened label? VR?, C? or something else?
     
  6. Corrie

    Corrie New Member

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    KeepItSimpleStupid - there is no variable resistor on there, think you are seeing the lil glob of silicon gel, not sure what you mean by silk screened label...

    anyway, sorry about the bad pic, here is slightly better one:


    [​IMG]

    You can see the scorching on the back (top pic), that obviously wasn't the problem as it wasn't there before the light show lol.
     
  7. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    OK, fooled by a glob of glue. But, there is a black discoloration in the middle of your 1st picture AND the two left pins of the bridge might be cold soldered. Note the ring. Can you wiggle the bridge and see the pad move? See if there is a designator under the wire. Like F1, L1.

    Most of the componets seem identifyable identifyable. The 1R0 is a 1 ohm resistor. The 104 is 10+4 zeros ohms or 100K ohms.

    Do you havea DVM with a diode test or even an ohms function. Look up the datasheet for the bridge and check for shorts or a 0.6V drop in one direction. You should see how the diodes are arranged. It should at least look like this: http://www.mouser.com/ds/2/427/kbu8-240448.pdf

    Depending on your mains or if this is auto switching you should have about 168 or 338 across the capacitor.

    For now, I suspect either a bad bridge and/or 1 or 2 bad joints. The black thing looks suspicious. What's the designation?
     
  8. Musicmanager

    Musicmanager Active Member

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    Hi

    I would give the underside of that board a clean with a stiff toothbrush and some Isopropyl Alcohol - that sooty deposit is likely to be conductive; Also, check the integrity of the soldering - the two innermost pins of the rectifier, particularly, look cracked to me ..

    S
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    As professional service engineer we won't touch Dyson, horrible stuff :p
     
  10. Pommie

    Pommie Well-Known Member Most Helpful Member

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    Nigel, Can you qualify that? In what way are they horrible? Bad components choice, design, serviceability etc.? I've never touched (fixed) anything Dyson but assumed, wrongly it seems, that they were very good.

    Mike.
     
  11. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    All of those :D

    They are made from horrible plastic that all clips together, very difficult to get apart (often requiring special tools), and difficult to work on once you get them apart.

    Most of the independent trade doesn't even sell them any more, mostly it's the large multiples (who don't offer any service facilities) that do.
     
  12. MaxHeadRoom78

    MaxHeadRoom78 Active Member

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    Maybe you got the Chinese knock-off version, DieSoon?:)
    Max.
     
  13. Corrie

    Corrie New Member

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    KeepItSimpleStupid - Checked the bridge again, just diode test, but it looked fine, checked all the solder joints..

    Musicmanager - Cleaned it up and re-soldered any questionable joints...

    Plugged it back in and its now truly dead, totally fried it. I'm getting a replacement board, will perform autopsy on this one when i have time, if i find out what the problem was will let you know..

    In the mean time, my only other concern is the motor, in all this i don't think it turned once, i put the multimeter over the brushes in resistance (setting 200) and turned the motor manually recording the resistance changes, lowest was 35 highest was 177 does that sound off for a 240v DC motor?
     
  14. MaxHeadRoom78

    MaxHeadRoom78 Active Member

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    If a regular Universal motor, hook it up direct to 240vac or if nervous use an automotive battery to see if it turns OK polarity does not matter.
    If it is a PM DC motor, then use the car battery.
    Max.
     
  15. Corrie

    Corrie New Member

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    MaxHeadRoom78 - thanks, didn't think of that; the motor won't turn, fully charged 12v battery on there and nothing. I'm thinking what has happened is the coils are fused enough to lower the overall resistance enough boost the current and knackered the board, basically the vacuum cleaner burnt out its motor and is so poorly designed it killed itself.

    Shame i didn't test the motor earlier, but live and learn :)

    thank you all who offered suggestions, i do appreciate it.
     
  16. BVQ

    BVQ New Member

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    I thought that I would add to this thread in the light of what I have just seen. A friend asked me to look at his failed DC24 for which he had already replaced the motor without success. I took a look at the small circuit board and discovered that the two inductors on the underside of the board were both open circuit. I cannot determine the part number of these devices but they were fitted for EMC reasons. The fact that they blew before the 8A bridge rectifier suggests that they were rated at less than 8A. Components of that size are unlikely to be able to pass more than about 3A. Assuming that these are open circuit they can be replaced with a couple of pieces of tinned copper wire to prove that the motor is OK. To reinstate the original EMC performance a couple of inductors would have to be purchased from RS/Farnell/Digikey/Mouser, etc. Make sure that the underside of the push on connector insulated boot is not burnt through.

    upload_2017-8-3_16-13-42.png
     
    Last edited: Aug 3, 2017
  17. GromTag

    GromTag Active Member

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    Chip inductors are cheaper than fuses.
     
  18. pfofit

    pfofit Member

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    2 year old thread, however, buddy "had" bigger problems as the main traces to the ac input of the bridge popped right off the board, inductors burnt, as well the fusible? resistor died as well. Bad joints on bridge.

    A shorted motor , or a shorted bridge ?
    cheers

    Dyson002.jpg
     
  19. Tabbypig

    Tabbypig New Member

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    BVQ: thanks for your contribution; helped me.:)
    I too had L1 and L2 fried and really don't know if these are tiny inductors or just fuse links. Either way; replaced them with 5A fuse wire links and all is well. DC24 PCB L1 L2 Fried.JPG DC24 PCB L1 L2 Linked.JPG
     

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