I inherited this a year ago and it has been a good vacuum cleaner with
it's own little electric motor to power the brush head.
It has stopped rotating the motorhead without warning and a red LED is
glowing when power is switched to the head.
I have stripped the head and it uses a Domel 230VDC motor via a PCB
which has the LED. This motor rotates slowly when 12VDC is applied.
The two leads coming to the head measure 90VDC on a moving coil meter.
I'm thinking the head and PCB are probably OK but some diodes have
gone open circuit in the power supply.
On Fri, 21 Oct 2016 11:31:26 +0100, email@example.com wrote:
(Don't just Google Motorhead or you might get a completely different
answer!) I would give them a ring - nothing to lose. There is a good
Dyson repairer near me and I am sure there must be many more. Maybe
they could cannibalise another machine?
I did go through the fault routine on the Dyson website and having
established it wasn't a stuck brush did ring them as the web page
suggested. The only response I got was Dyson no longer support the
machine though I could be entitled to a discount on a new model.
My father was a fan of Dyson so he bought my mother the vacuum
cleaner, he died over 10 years ago so it is old.
I inherited a Dyson washing machine from him and it was nothing but
trouble, after the second control panel failed I binned it. I swore
not to buy another Dyson product, though I have had some decent
upright vacuum cleaners of theirs as gifts, which have been passed on
to family members.
So rather than waste this one I aim to try and repair the motorhead
function, though it still works as a normal vacuum cleaner.
On Fri, 21 Oct 2016 14:11:43 +0100, firstname.lastname@example.org wrote:
I believe the washing machine was discontinued.
I would still check with a local third party Dyson repairer (if you
have one) to see if he/she could point you in the right direction.
They might have a spare lying at the back for all you know.
He was in an interview about a year or so back where he admitted that the
washing machine was a bit too complicated and there were too many bits to
fail if the contra rotating drums got stuck or several other special bits
went south. It was also not very useful as it never fitted in a standard
sized hole in kitchen units.
On the brush issue, what exactly does the pcb do? If an led glows then I'd
have supposed that the fault was an over current safety shut down mode. as a
stuck brush would look like tat and the circuit would disconnect the motor
and light the led. I've seen similar things on other devices like blenders
From the Sofa of Brian Gaff Reply address is active
Remember, if you don't like where I post
I don't know, it seems to have a 1 microFarad capacitor across the
motor terminals , 2 inductances, 2 diodes and various resistors.
I can post a picture but what picture hosting sites are available now?
Yes but I think the fault is in the supply before it gets to the PCB.
I suspect there is a power supply in the handle near the switch but
the trouble with Dysons is getting them apart without breaking
anything. They are often assembled with plastic clip lugs in blind
holes and if they won't pull apart something else gives or the lug
I'll search the forum Mike suggested.
I've already stripped down to the main motor and no sign of any active
Thus neatly proving that the motor is working ok. :-)
Actually, there's every chance you've hit the nail right on the head!
Most likely (assuming there's no fancy speed controller included), the
"Power Supply" is nothing more than a bridge rectifier (a module or 4
discreet 1N4007 or similar diodes).
From your description, my inference is that the PCB in question is in
the vacuum cleaner itself rather than in the motor head. If you repeat
your test with your moving coil multimeter using a suitable AC voltage
range (say 5 to 6 hundred volt scale) and take readings with the test
probes applied each way around, you should see only a very low reverse
reading when applied the wrong way round and an ac voltage reading close
to *double* the expected mains voltage when the rectifier is working as a
fullwave rectifier. If the rectifier has an open circuit diode as your
voltage reading suggests, it will be acting as a halfwave rectifier and
the meter will then read just slightly less than the AC voltage feeding
If this turns out to be the case, 1N4007 diodes or 1A mains bridge
rectifier modules are readily available and cheap. All you then need is a
soldering iron, some multicore solder, a cheap desoldering pump or small
flat bladed screwdriver, long nose pliers and the skill to use them to
remove the faulty component(s) and solder in the replacements.
Alternatively if you lack such tools, find someone who does have such kit
and the necessary skills. :-)
 This assumes that the rectified output voltage is not subjected to a
smoothing circuit such as a 400v rated capacitor placed across its DC
output terminals - a pretty safe bet in this case since the 230v DC motor
will work perfectly fine with an unsmoothed rectified supply without
incurring the needless expense of an extra failure prone component which
itself places additional stress on the rectifier.
 If one of the rectifier diodes has failed open circuit, you'll only
see the expected mains voltage reading. The reason for this behaviour
with the classic moving coil multimeter is due to the AC voltage ranges
relying on half wave rectification of the test voltage which halves the
average current, necessitating an approximate halving of the multiplier
resistances used for each ac voltage range (approximate because the meter
reads the average voltage but is calibrated to show the RMS value which
is about 10% higher, requiring a similar further 10% reduction in
multiplier resistance values to compensate.
A typical 20Kohms per DC volt multimeter will have a 10K ohm per AC volt
sensitivity (the moving coil meter circuit is either desensitised
slightly on its DC volts and amps range to make the half ohms per volt
sensitivity figure for the AC ranges true or else the given AC ohms per
volt figure is simply a rounded up approximation.
When you connect an old fashioned analogue multimeter to a dc test
voltage using one of its AC voltage ranges (say a 12v SLA measured on the
30 or 50 volt AC range) the reading will slightly double that which was
read on the DC volts range. If you test a halfwave rectified DC supply,
the AC volts reading will be only slightly less than the AC voltage
feeding the rectifier diode. Testing with a fullwave rectified DC voltage
will double this reading for pretty much the same reason that measuring
12vdc on a 30vAC range gives a reading of just over 25 volt.
No the PCB is actually in the head, it seems to be supplied with DC
via a 4 position switch in the handle which I have not been able to
open up to investigate. The first position is all off, the second is
vacuum only , the third is vacuum and motor head brush which gives a
red light on the motor head PCB and the fourth is supposed to just
rotate the head slowly. I took one input terminal off the PCB (and
broke the push on crimp in doing so) and tested the voltage in
positions 3 and 4. Three powers up the main vacuum motor and supplies
only a few tens of VDC, 4 gives about 90VDC, this suggests a problem
in the switch.
As you say it reads over 200V on an AC scale with terminals one way
and zero the other.
Looking at the forum Mike suggested the is a common problem with this
switch but no power supply components are mentioned.
I just need to get it apart and look.
There's a good chance that the switch feeds the power to a bridge
rectifier in positions 3 & 4. Using a 2 pole 4 way switch will allow one
of the brush head motor wires to be transferred from a DC output terminal
(+ve or -ve) on the rectifier to one of its ac input terminals (~),
effectively turning the circuit into a half-wave rectifier cutting the
unsmoothed averaged DC voltage in half. It's a cheap and crude (but
effective) form of DC motor speed control.
The problem could be a switch or rectifier fault or just simply a broken
or disconnected wire between the switch and the brush head motor circuit.
You'll have to gain access to the switch wiring if you want to pursue
this fault finding exercise any further.
 This slow speed circuit might include a dropper resistor if half
speed isn't quite slow enough on its own account. It's also worth bearing
in mind that another possible way to feed that dc motor with half voltage
is to switch the rectifier's ac input terminal from full mains voltage to
half mains voltage available at the join between the two field windings
on the main universal motor.
Indeed, if the desired motor speeds are full and quarter speed, the two
methods can be combined on the fourth position if a three pole 4 way
switch is used. I can't think of a way of doing this with just a 2 pole 4
way switch off the top of my head but if there's a way, you can bet your
life that Dyson would have thought of it. :-)
Picture of PCB in the handle adjacent to the switch here
The diodes seem to check out with .75V forward voltage and no reverse
It seems to have a triac in the circuit, I cannot get the switch out
to see where the wires go.
Looking at the picture, I can't see any signs of a triac (nor any place
on that PCB where one might lie hidden from view unless it's mounted on
the reverse side).
The circled area marked "RV1" looks like this Variable Resistor
component may have been replaced by a couple of resistors located at the
switch (it's hard to tell, but it looks like the mounting holes are wired
back to the switch).
The two electrolytic caps at the opposite end of the board look
suspiciously like they may be a couple of 200vdc rated caps wired in
series to provide a smoothed 350v HT supply for a switching converter
(perhaps there *are* additional surface mount components on the underside
after all but the PCB's appearance suggests otherwise).
Apart from the 6 rectifier diodes and a small glass diode (probably a
zenner), I can see what looks like a 15 ohm (green bodied) resistor with
what looks like a smaller 22K ohm resistor alongside. The 15 ohm resistor
is probably a current inrush limiter for the 350v HT rectifier circuit
and the 22K looks like it feeds current to that glass diode (zenner?).
The remaining components could both be small capacitors. The black one
certainly is but the red "ceramic disk" might be a spike clipping
varistor (although, ime, these are usually coloured blue).
Unfortunately, without a set of decent photos to show both sides of the
PCB *clearly* (the wires should have been moved aside or a better angle
of shot chosen to make it clear as to what and how many wires are
connected to the board), it's impossible to work out exactly how this
functions as a DC motor speed controller and what possible failure mode
could have led to the symptoms and measurements you've taken with your
moving coil multimeter. We can take educated guesses but unless someone
familiar with the innards of a DC05 recognises that board, an educated
guess is the best you're going to get.
If you can't track down a service manual with circuit diagrams for that
model of vacuum cleaner, the wiring will have to traced (both the PCB
circuit and the rest of the wiring including switches and motors etc) to
recreate a circuit diagram in order to continue the quest to effect a
Unless you can't actually see the switch connections, it might be worth
posting a few more photos (uncluttered views both sides of the board and
a photo or two of the switch wiring). I'm guessing you'll find a couple
of resistors wired directly onto the switch contacts once you gain access
(if you have access to one of those cheap snake (bore-scope) cameras, you
might be able get enough of a view to determine whether or not this is
<http://dysonrepairmanuals.com/DC05%20Folder/DC05%20page.html is a good
starting point of reference which, at a glance, looks quite useful. :-)
However, further googling got me no nearer, as promised in the link
above, to tracking down a service manual or circuit diagram so it looks
like you'll have to trace the circuitry yourself to create a full circuit
diagram along with an accurate parts list. Once you have this, the only
likely proprietary bits will be the switch and the motor. The motor is
apparently readily available (take heed of the advice).
I'm not so sure about the switch - you can google the various spare
parts traders' sites yourself if the switch proves to be the fault. The
fact that the 230vdc motor still runs slowly on a few dozen volts
suggests the problem isn't there (BICBW).
Good luck & HTH
The black rectangle with a heat sink in the side above C2, what is
RV1 is the red blob
Yes I thought it was a zener too.
I will get some better photos up and see if I can trace the circuit
and also the other PCB in the motorhead but as I only want the brush
to work would there be any harm in abandoning the Dyson PCB and
feeding it with a simple 400V rated bridge rectifier off a separate
I can't see any evidence of a heatsink from that angle. However, it's
possible that what I thought was a small 100nF capacitor might well be a
plastic power transistor or triac with the heatsink tab chopped off flush
to the encapsulation.
Ok, now you've given me another clue, I can see how that would fit. The
red blob, which I have to assume is a varistor in spite of it not being
blue, looks like it has been flipped up from its intended laid down flat
mounting position as implied by the silk screen print.
Assuming that the "100nF capacitor" is actually a triac, I doubt you'll
get away with just a simple bridge rectifier. However, if you're going to
experiment, that 400v rating should be for the ac input voltage based on
the assumption that the output will be connected to a simple reservoir
smoothing capacitor ripple filter.
The rule of thumb in this case is to rate the diode PIV at 3 times the
maximum rms input voltage since each diode element in the rectifier
bridge will be subjected to twice the peak inverse voltage (1.414 times
the rms ac voltage) due to the peak voltage stored by the smoothing
capacitor. Assuming a perfect sine wave form on a 240v ac supply, each
diode will be subjected to a PIV of 2.828 * 240 volts, just under 680
volts! With an rms voltage at its upper 265v limit, the PIV will be a
whisker under 750 volts.
However, the Public Supply Utility voltage is far from a perfect sine
wave, typically looking like a slightly flat topped sine wave which will
reduce the theoretically calculated peak voltages by a few percent.
Even so, it's always best to use an even higher voltage rating, in this
case 800v PIV, to allow for spike voltages and sub station voltage
controller faults that allow the PSU to go above the 265v rms limit
(unless, of course you deliberately choose a 700 PIV rated diode to
protect the expensive HT switching transistors against such over-volting
events in an act of self sacrifice to blast the safety fuse to
smithereens - diodes and fuses are a damn sight cheaper and easier to
replace than HT switching transistors!).
The gratitude is appreciated. :-)
If you do decide to post any more pictures, try and compose the shots so
as to maximise clarity. Provide two or more angles of view, bending any
wires aside if necessary and pay attention to the lighting which can make
a huge difference to the clarity of the images.
Digital photography allows anyone to take as many photos as they fancy
of such a "Still Life" subject as this. You can easily fire off half a
dozen or more at various angles and lighting conditions from which to
pick out the best two or three to post up on a web site for us all to
peruse and admire.
Oh, and just one final point. As far as I can make out, there's no signs
of obvious component damage on that little PCB but, of course triacs and
diodes can develop faults without any obvious signs of failure. However,
when we're dealing with circuits carrying mains voltages, any such
internal failures tend to result in physical damage, either co-lateral or
self inflicted since the most likely failure mode tends not to be a fail
safe open circuit state but rather a dramatic pyrotechnical short
If as you surmise, there's a triac on the circuit board, it must be
controlled from the switch using a couple of resistors to control the
triggering delay. Such resistors are typically high value resistors of a
low wattage rating. If they've been soldered straight onto the switch
contacts, it's possible they may have been damaged by the action of the
switch sending shockwaves into the contact tags. If the resistors have
been soldered to those contacts via very short leads, they may well have
failed as a result of the accumulated cycles of use over the years. IOW,
don't ignore such components which must exist somewhere external to that
I've returned to this after a short break.
I looked at the circuit board by the switch again and realised it is
likely to be a speed control for the brush in the Zorb (rotating no
vacuum) position, so irrelevant to the problem.
Is a picture of what I now think is the power supply to the motor in
the head. The power comes in from the let and out to the motor at the
bottom. The LED is cropped but at the top. It seems to have an
integrated full wave rectifier, some inductances for smoothing and
capacitors plus an unidentified black blob
When I apply 230V directly to the power in the LED glows red and the
motor does not run.
I have also checked the switch and I think some contacts have burned
out but that doesn't account for the fact that the motor won't run
when 230V is applied to the board directly.
the underside of the board
If the black blob you're referring to is what looks like a disk mounted
on edge to the board, that's most likely a VDR to trim any transient
I see the rectifier module (W08M) of which two of its diode elements
form a second fullwave rectifier in conjunction with the two back to back
discrete diodes on the left which act as an additional positive output
terminal feeding one of the two 33K ohm 1W resistors used as a DC ballast
to feed that red LED with ca 5mA of current.
The white oblong component at the bottom is obviously a high voltage
capacitor across the motor terminals and this, in conjunction with the
two inductors forms an RFI filter to suppress interference produced by
the motor's brush gear.
The 2.7Mohm 1/2W resistor (RHS - possibly 2.0Mohm if that dark purple
band is actually black) is effectively wired across the 400vdc rated
smoothing cap at the top to act as a safety discharge resistor in the
event of the circuit having been energised with the motor disconnected or
open circuit just prior to being handled.
In which case, it looks like that rectifier module (W08M) must have gone
faulty. The inductors are the only components in series with the motor
supply and they both look to be in robust full health (they should each
show a short circuit reading when tested on the resistance measuring
scale of a DMM or MM (mains disconnected!). I'm assuming that the motor
is still in full working order as your OP suggested (turning slowly with
a few tens of volts applied - hopefully, slowly and *steadily*)
That picture would have been more useful if you had created a mirror
image (post processed in the GIMP or Photoshop) or had simply used a
mirror to take the photo in the first place!
 The only fault I can think of that would still allow the LED to light
up (the difference between full and half brightness can be difficult to
distinguish by memory alone) would require that both positive diode
elements to go open circuit in the bridge rectifier module (W08M).
It says bTh 100 on it, a search suggests it may be a varistor.
I have checked the forward voltages and the integrated full wave
rectifier is okay. I thought the other two diodes just rectified the
supply for a voltage divider that triggered the LED, I think the LED
has two colours, red (at present) and green when working normally.
Yes I see this.
I see the resistor as brown black green gold, 1 M Ohm but I see what
you say about a discharge resistor
It turns steadily with 12V and actually runs up fine with 230V ac but
I think the above circuit is sensing something wrong with it and
somehow inhibiting its supply.
I think this is not the case and that the LED in fact contains red and
green elements but not a clue what switches them.
I'm going boss eyed trying to draw the circuit which I can upload if
it would help in further diagnosis?
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