The main motor on our washing machine is no longer working - neither on
wash nor spin cycles. It runs through the programmes OK apart from that,
so I suspect the motor controller.

Machine is a Bosch WAE28467UK/14. On looking at the power side of
the controller board, there is what I think is a diode with suspicious
carbonisation around one end:
http://www.leverton.org/temp/P8300049_small.png
(there is more carbon on the board off to the right of the pic, which
has left a clear shadow around the legs of the mini-transformer making
it fairly clear that the source is that component with the blackened end).

I'm assuming it's a diode cos I don't know what else it looks like.
Electrically it seems odd though (I'm no electronics engineer I have to
admit). I only have a cheap ten-quid digital multimeter, which starts
off showing a middling resistance (100 ohm or so) but rises within
a second or so to open circuit - same whichever way round I test it.
The behaviour is more like a capacitor, but I've never seen one like that.
Both the diode-like thingys visible in the pic behave the same.

The mini transformer seems OK I think, both primary and 2ndary coils have
a small but non-zero DC resistance. The bigger caps just visible look OK,
no bulging or distortion. The other visible diode also looks OK, as do
the two resistors and the power transistor, which is about all there is
on this side of the board. Nothing on the other, surface mount logic,
side of the board is discoloured.

So - am I right this is a diode ? If it's blown, why does it show the
same resistance characteristics as the apparently good one ? What type
am I likely to need to replace it with ? Any help would be appreciated,
as I don't want to have to pay 60 to 100 quid for a new board if it's
only got a pain in the diodes down its left side ...

Thanks

Nick
--
Serendipity: http://www.leverton.org/blosxom (last update 29th March 2010)
"The Internet, a sort of ersatz counterfeit of real life"
-- Janet Street-Porter, BBC2, 19th March 1996

"Nick Leverton" wrote in message ...
The main motor on our washing machine is no longer working - neither on
wash nor spin cycles. It runs through the programmes OK apart from that,
so I suspect the motor controller.

Machine is a Bosch WAE28467UK/14. On looking at the power side of
the controller board, there is what I think is a diode with suspicious
carbonisation around one end:
http://www.leverton.org/temp/P8300049_small.png
(there is more carbon on the board off to the right of the pic, which
has left a clear shadow around the legs of the mini-transformer making
it fairly clear that the source is that component with the blackened end).

I'm assuming it's a diode cos I don't know what else it looks like.
Electrically it seems odd though (I'm no electronics engineer I have to
admit). I only have a cheap ten-quid digital multimeter, which starts
off showing a middling resistance (100 ohm or so) but rises within
a second or so to open circuit - same whichever way round I test it.
The behaviour is more like a capacitor, but I've never seen one like that.
Both the diode-like thingys visible in the pic behave the same.

The mini transformer seems OK I think, both primary and 2ndary coils have
a small but non-zero DC resistance. The bigger caps just visible look OK,
no bulging or distortion. The other visible diode also looks OK, as do
the two resistors and the power transistor, which is about all there is
on this side of the board. Nothing on the other, surface mount logic,
side of the board is discoloured.

So - am I right this is a diode ? If it's blown, why does it show the
same resistance characteristics as the apparently good one ? What type
am I likely to need to replace it with ? Any help would be appreciated,
as I don't want to have to pay 60 to 100 quid for a new board if it's
only got a pain in the diodes down its left side ...

You can't use the resistance range of a digital multimeter to measure a good diode or transistor
(but it might prove you have a faulty one)
Even a cheap meter should have a diode test range. The readout is in milivolts, not ohms if good
a diode will rad about 700mV or 0.7V in one direction and much higher or unreadable in the other.
Your pic isn't quite clear enough but it looks knackered and will probably fall apart if you unsolder
it, so read all the markings first so we can find a replacement.
The diode might not be the only casualty though.

--
Graham.

%Profound_observation%

On 31/08/2011 00:39, Nick Leverton wrote:

What he said, but if that is a "fast" diode check that cap near it as well.

Lee

"Nick Leverton" wrote in message
...
The main motor on our washing machine is no longer working - neither on
wash nor spin cycles.
SNIPPED

Apologies for asking the obvious, but have you checked the brushes on the
motor?
I failed to check the brushes on a Hotpoint with a non-functioning motor
once.

Often though the soldering or the copper track itslef does get warm when its
quite old and may well be a red herring. I assume you have proven the motor
is OK in some fashion?

Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Nick Leverton" wrote in message
...
The main motor on our washing machine is no longer working - neither on
wash nor spin cycles. It runs through the programmes OK apart from that,
so I suspect the motor controller.

Machine is a Bosch WAE28467UK/14. On looking at the power side of
the controller board, there is what I think is a diode with suspicious
carbonisation around one end:
http://www.leverton.org/temp/P8300049_small.png
(there is more carbon on the board off to the right of the pic, which
has left a clear shadow around the legs of the mini-transformer making
it fairly clear that the source is that component with the blackened end).

I'm assuming it's a diode cos I don't know what else it looks like.
Electrically it seems odd though (I'm no electronics engineer I have to
admit). I only have a cheap ten-quid digital multimeter, which starts
off showing a middling resistance (100 ohm or so) but rises within
a second or so to open circuit - same whichever way round I test it.
The behaviour is more like a capacitor, but I've never seen one like that.
Both the diode-like thingys visible in the pic behave the same.

The mini transformer seems OK I think, both primary and 2ndary coils have
a small but non-zero DC resistance. The bigger caps just visible look OK,
no bulging or distortion. The other visible diode also looks OK, as do
the two resistors and the power transistor, which is about all there is
on this side of the board. Nothing on the other, surface mount logic,
side of the board is discoloured.

So - am I right this is a diode ? If it's blown, why does it show the
same resistance characteristics as the apparently good one ? What type
am I likely to need to replace it with ? Any help would be appreciated,
as I don't want to have to pay 60 to 100 quid for a new board if it's
only got a pain in the diodes down its left side ...

Thanks

Nick
--
Serendipity: http://www.leverton.org/blosxom (last update 29th March 2010)
"The Internet, a sort of ersatz counterfeit of real life"
-- Janet Street-Porter, BBC2, 19th March 1996

In article ,
Nick Leverton wrote:
I'm assuming it's a diode cos I don't know what else it looks like.
Electrically it seems odd though (I'm no electronics engineer I have to
admit). I only have a cheap ten-quid digital multimeter, which starts
off showing a middling resistance (100 ohm or so) but rises within a
second or so to open circuit - same whichever way round I test it. The
behaviour is more like a capacitor, but I've never seen one like that.
Both the diode-like thingys visible in the pic behave the same.

Most DVMs have a diode test function. If they have, there will be a diode
symbol indicating it.

Disconnect one end of the diode and connect the DVM. Leaving it in circuit
can give a false reading. The end of the diode with a bar is the cathode,
which connects to the black lead on the DVM. You should get a reading of
approx 0.7 volts. This is the forward voltage drop of a working diode.

--
*All men are idiots, and I married their King.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
"BluntChisel" writes:

"Nick Leverton" wrote in message
...
The main motor on our washing machine is no longer working - neither on
wash nor spin cycles.
SNIPPED

Apologies for asking the obvious, but have you checked the brushes on the
motor?
I failed to check the brushes on a Hotpoint with a non-functioning motor
once.

The dirt on the board/diode doesn't look to me like it came from
the diode. When components let go, the scorch marks radiate outwards.
The dirt on that diode looks like it came through the gap between the
capacitor and inductor. It came through slowly enough to be deposited
as a bow-wave, so it's probably just dropped out of the airflow during
normal operation of the machine. (Dirt is generate by motor brushes
wearing, and the belt wearing on the pullies, and airflow generated
by the various rotating parts.) Also, an exploding semiconductor
doesn't leave a bow-wave type deposit - the force is too high.
So, without a more detailed examination, I would suggest that dirt
is a red herring, but I would want a more detailed examination, eg
around the other side of the diode and up the sides of the capacitor
and inductor.

I would also suggest motor brushes, and also the possibility of a
broken conductor in the wiring loom to the motor. I've had motor
drive triacs go (caused by failing motor brush), but in my case
that didn't result in any visible damage as it just went open-circuit.
I diagnosed the issues by checking for voltage at the motor, and
tracing back, but this is not necessarily very safe to do, depending
on how easy it is to access the parts, and if there are any exposed
live parts.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Tue, 30 Aug 2011 23:39:15 +0000 (UTC), Nick Leverton
wrote:

It runs through the programmes OK apart from that,
so I suspect the motor controller.

While you are looking at the control board look carefully at the top
of all the capacitors, they should be flat. If any are bulging
upwards they have probably failed (or at least should be renewed while
you have the chance).

On Wed, 31 Aug 2011 09:41:00 +0000, Andrew Gabriel wrote:

In article ,
"BluntChisel" writes:

"Nick Leverton" wrote in message
...
The main motor on our washing machine is no longer working - neither
on wash nor spin cycles.
SNIPPED

Apologies for asking the obvious, but have you checked the brushes on
the motor?
I failed to check the brushes on a Hotpoint with a non-functioning
motor once.

The dirt on the board/diode doesn't look to me like it came from the
diode. When components let go, the scorch marks radiate outwards.

Agreed.

I don't remember ever seeing a diode fail where it's emitted stuff,
either. Died with no visible damage, yes, and blown completely apart,
yes, but not like that.

If that discolouration on the leg were due to severe overheat then I'd
expect more visible damage to the board, too (and doubtless the
associated PCB trace on the underside).

The
dirt on that diode looks like it came through the gap between the
capacitor and inductor.

That, or it's a component failure elsewhere.

cheers

Jules

On Aug 31, 12:39*am, Nick Leverton wrote:
The main motor on our washing machine is no longer working - neither on
wash nor spin cycles. *It runs through the programmes OK apart from that,
so I suspect the motor controller.

Machine is a Bosch WAE28467UK/14. *On looking at the power side of
the controller board, there is what I think is a diode with suspicious
carbonisation around one end:http://www.leverton.org/temp/P8300049_small.png
(there is more carbon on the board off to the right of the pic, which
has left a clear shadow around the legs of the mini-transformer making
it fairly clear that the source is that component with the blackened end)..

I'm assuming it's a diode cos I don't know what else it looks like.
Electrically it seems odd though (I'm no electronics engineer I have to
admit). *I only have a cheap ten-quid digital multimeter, which starts
off showing a middling resistance (100 ohm or so) but rises within
a second or so to open circuit - same whichever way round I test it.
The behaviour is more like a capacitor, but I've never seen one like that..
Both the diode-like thingys visible in the pic behave the same.

The mini transformer seems OK I think, both primary and 2ndary coils have
a small but non-zero DC resistance. *The bigger caps just visible look OK,
no bulging or distortion. *The other visible diode also looks OK, as do
the two resistors and the power transistor, which is about all there is
on this side of the board. *Nothing on the other, surface mount logic,
side of the board is discoloured.

So - am I right this is a diode ? *If it's blown, why does it show the
same resistance characteristics as the apparently good one ? *What type
am I likely to need to replace it with ? *Any help would be appreciated,
as I don't want to have to pay 60 to 100 quid for a new board if it's
only got a pain in the diodes down its left side ...

Thanks

Nick

Yes its a diode, and blackening of diode legs is normal and common.
You cant measure a diode while its in circuit, the resulting readings
are meaningless. The reliable approach to troubleshooting is to get
the circuit diagram and a multimeter, and find out where things are
working ok and where they're not.


NT

In article , Nick Leverton
scribeth thus
The main motor on our washing machine is no longer working - neither on
wash nor spin cycles. It runs through the programmes OK apart from that,
so I suspect the motor controller.


Check the brushes I'd go for that first thing most likely fault;!...
Machine is a Bosch WAE28467UK/14. On looking at the power side of

Don't bother with that check to olde carbons..
--
Tony Sayer