Capacitor

[djrock]

Hello, I am replacing capacitors in a old food mixer. Is it ok to replace a 0.15uf cap with a 0.22uf cap?


Thankyou

djrock

[starfury1]

Re: Capacitor

thing with that is its probably a mains operated device Meaning you must use approved caps for this

Not knowing exactly what the caps being use for (no idea whats in a food mixer)
it would probably be ok but it must be the same type or an equivalent replacement type

Post a photo of the guts and its location and I am sure someone will be able to tell you

Whats that you say ?,
you want to how to post photos here
check this thread of Willawake's (forum mod) on how to do it.

https://www.badcaps.net/forum/showthread.php?t=1868

Start Legal Rant

Mains Voltages are potentially Deadly so all disclaimers apply here "You Do At Your Own Risk
(be advised that depending on were you are it may be illegal for you to do this work)
End Legal Rant
Just covering mine and the forums rear end here.

Welcome

Cheers

[djrock]

Re: Capacitor

Hello, I don't have a photo of the guts of it but i have the spec and a similar photo of them.

This is the spec taken from the bad caps.

0.15uf 250v 3.8Mhz
0.047uf 40/085/56 PME 271M547

Both I think appeared to be made by Rifa and are like the ones in this Link.

The ones I got to replace them are like these http://www.maplin.co.uk/images/300/bx84f_bx70m.jpg.
I told the guy the voltage, the cap value, what it was needed for and thats the caps he gave me.

djrock

[starfury1]

Re: Capacitor

I wouldn't be the best person to answer this one so you really might want to wait
for a better reply on this.

One question you should ask yourself is "WHY" did they fail Why do you need to replace them

There could be another failure just waiting to bite you

if you look at you "link" photo you will see lots stamps on these caps the clear ones
These are Agency safety approval stamps for capacitors used with Electrical Mains supply

So you need to replace with this type of capacitor that is type approved.

The maplin link, these look like they are a high voltage polyester, more commonly know as greencaps (or orange drops I think from memory)
(going by the photos)

These would as far as I am aware be "Unsuitable" for this application.

The caps you need to get are know as either X or Y caps depending on there location inside that device.

OUTLINE OF CAPACITOR CLASS RATINGS
Capacitor are classified by the IEC into two
categories (these designations are used by most
European countries).
Class Y: Capacitors used in applications where
damage to the capacitor may involve danger of
electrical shock.
Class X: Capacitors used in applications where
damage to the capacitor will not lead to the danger
of electrical shock.

From this PDF HERE

I personally would "NOT" use those caps you got
unless they are specifically for X or Y Class use and I very much doubt they are.
Going by your links

EDIT:
I notice you told the guy what they were for so you need to check they are type approved
(caps can come in different packages)

These are issues of SAFETY to "human life & property" so you MUST used the correct type of caps

To be brutally honest
these type of repairs are best left to Properly Qualified Trained Technicians.
who can check for other possible fault conditions and are equipped to do so.

I can understand why people what to repair things them selfs but sometimes it really best to leave it to the professionals

HTH

Cheers

[starfury1]

Re: Capacitor

just on PME 271

Multi-layer metallized paper. Encapsulated
and impregnated in self-extinguishing material
meeting the requirements of UL 94V-0.

Here is a PDF Link

it appears to be Class X2 from the pdf

not sure on the 0.15UF 250V thought

HTH

Cheers

[djrock]

Re: Capacitor

Hello, The mixer (Kenwood Chef A901P) does still work but it's stuck on maximum speed and I have read that the traic can do this.
I think due to the triac failing has caused the capacitors to fail.

The caps I have been given have no safety markings, which as you said can't be a good thing. Would these cap be ok Link?
They are class x2 and approved but will it matter that they are 275vac not 250vac?

From what I can see the mixer does not appear to be very complicated electrical wise (2 caps, 2 resistors and a triac)
so I can see one reason why people still want them because they don't heavily rely on electrical components.

Thankyou

djrock

[kikkoman]

Re: Capacitor

looks good.
a (slightly) higher voltage rating is no problem here. WIMA is an established brand, too.

[djrock]

Re: Capacitor

looks good.
a (slightly) higher voltage rating is no problem here. WIMA is an established brand, too.

What about the rating? I can't get a 0.15uf so is it ok to fit a 0.22uf or a 0.1uf? Will the capacitance tolerance matter since I think the originals were 10% but the Wima's are 20%?

Thankyou

djrock

[gdement]

Re: Capacitor

What about the rating? I can't get a 0.15uf so is it ok to fit a 0.22uf or a 0.1uf? Will the capacitance tolerance matter since I think the originals were 10% but the Wima's are 20%?

Thankyou

djrock

I don't know anything about this type of thing. But if the original cap was 10% tolerance, that makes me think the spec must have been important. Otherwise I'd expect them to use a more common 20% part.

[starfury1]

Re: Capacitor

thanks for the info...as I said, mostly you probably could use 0.22uf
but not totally sure of how its put together
so strictly speaking I don't know on the 0.15 uf

I did find a post here on that model
this seems to be a common type failure

EDIT did find mention 41 years????...well that would explain failure

2 resistors
larger one on left of Triac (near) 0.47uf (47nf) is said to be 56 Ohms
The other on the right is said to be 220 Ohm

heres the original post and yeah seem like you need to check all the components
for failure would be a good idea..mention of replacing brush too

http://www.howtomendit.com/answers.php?id=68470

another thread says caps are for suppression ..makes sense

http://www.mendmy.com/answers.php?id=111979

this post that there are no answer to might throw a bit of confusion in to the mix apparently different controllers

http://www.mendmy.com/answers.php?id=110223

seems to be a bit on googling around but unfortunately no photos could I find

anyway Hope this helps

cheers

[gonzo0815]

Re: Capacitor

Those caps are probably for reducing the dT/dV or in plain words to slow down the transient produced by the off or on switching (assuming the capacitor & resistor is in parallel with the triac).
A relay would arc and a triac would go short if voltage rises too fast. This kind of circuit is commonly called a snubber or RC snubber.

The fast rule is 1Ohm/V and 0,1uF/A. It is recommended to use some UL or similar approved metal paper capacitor either from X1, X2 or Y1, Y2 class.
The safety class is determined if there is an fuse before the capacitor and if it does connect to ground / safety ground or only from neutral to hot.
For an snubber i would say an X1 or x2 should be sufficient, as long as there is an fuse anywhere.

Generally, the value of the capacitor is not critical, but if the capacitor is increased to far, there is the possibility that the motor coil and the capacitor will act like an oscillating circuit, which is not particular good.
But if you can`t manage to get some 0.15uF capacitors or 150nF ones i would try the 0.22uF ones.

[djrock]

Re: Capacitor

Hello, Starfury1 The mixer could be about 25 years old. I have read most of the posts you have linked to. That's when I discovered it was a common fault that could be fix very easily.

I will be replacing the two resistors as well. The 220ohm is way out of spec and the 56ohm is fine but I am going to replace it anyway.

I was thinking about changing the brushes as well.

There's nothing to worry about the different controllers. Since you can get a new controller on a pcb. I think it could be for a newer motor.

I will try and take a picture and post it sometime tomorrow, which might help to identify what the caps are being used for and if the tolerance value is important.


Thankyou

djrock

[starfury1]

Re: Capacitor

No worries
Age was probably its demise, so that possibly rules out a secondary fault which was more my concern.
(although suppose its still possible the triac is gone)

Since its using a triac, which is probably chopping up the mains sine for speed control
EDIT seems one maybe for timing trigger point but not sure
My guess is that the caps are purely there to shut up EMI/RF crap

true thought, values are chosen for specific reasons and thats why you shouldn't stray from them unless you know what the effect of this will be

I dont fix these things
and triac theory is way rusty with me
(apart from the fact its more or less a bilateral switch that you can set the voltage trip point on at various levels in the waveform)

I dont know the circuit either, it seems to be crudely simple and that perhaps account for its reliability.

Looking at a PDF on Triac Control
that cap maybe being use to set the "trigger point"
(this could possibly explain the use of closer tolerance capacitors)
If so, then by using a larger cap you will change the trigger point




(Also note the use of a DIAC with the TRIAC)

http://www.play-hookey.com/semicondu...iac_triac.html

http://www.hobbyprojects.com/thyrist..._and_diac.html

No mention of a Diac being used in that controller?
(have to look into this ...like I said I have forgotten....these you do tend to find used with triacs.
They are open circuit till their trigger voltage is hit then go short circuit
using the term "'open short" loosely here.
(high resistance, low resistance would be better)

there are some pdf's and other interesting stuff of this link

http://www.educypedia.be/electronics...ronicsdiac.htm



if you can just draw a diagram of what connects to what for reference.
sometimes with photos its hard to see what connect to what if its skyhooked
but either would be of help to me as I don't know.

I did a bit of googling but didn't find anyone had posted a photo or a diagram

At this point I'll leave it
The links should help understand better how the thing works.
but I know it doesn't really answer your questions

Cheers

I edited out this bit but will leave it for my reference
if the 1n5f (0.15uf) is purely for EMI I see no reason not to use a 2n2nf (0.22uf)
10% jobs my have been all they could get at the time, Dont know

[starfury1]

Re: Capacitor

This might explain it a bit better

http://www.allaboutcircuits.com/vol_3/chpt_7/6.html

Firefox decided to play silly buggers and went on a go slow for some reason.

cheers

[gonzo0815]

Re: Capacitor

I don´t think that the caps are there for setting the trigger point, but sure w/o circuit it is all guesswork.
Trigger point is either set with a resistor voltage divider or an diac or with both.

[starfury1]

Re: Capacitor

in one of the forum links its stated for EMI surpression for both of them caps that is
(but No mention of diac use)

from the ST doc PDF link

Triggering with synchronization on the TRIAC voltage
The triggering circuit with synchronization across the TRIAC (See Figure 1 and Figure 2)
turns on the component at an angle β after the current drops to zero, such that
β = ω · Tr.
Time Tr is defined by the time constant (P + Rt)C.
ω = 2 · π · f with f = mains frequency.
Figure 1. Typical Circuit: synchronization across the TRIAC

==========================================================
Also if you look at the last link (separate post above) it shows a pot and cap and says;

"A simple lamp dimmer circuit is shown here, complete with the phase-shifting resistor-capacitor network necessary for after-peak firing."

thats why I thought possibly for triggering

true, no idea really and circuit is not known
I Have forgotten most everything with triacs
esp with regard to how you trigger them.

its guess work based on links, as you said.

Thanks for the reply Gonzo, every bit helps

Cheers

[gonzo0815]

Re: Capacitor

Sure in this circuit the capacitor is a snubber, to protect the Triac against high voltage spikes from the load switching. From another point of view it sure does reduce EMI too, but i assume that it is not necessarily needed for this task.
It does nothing else there and the circuit would work even without the capacitor.
But the triac may fail earlier, due to high voltage spikes and too fas voltage rise.
But i referred to the circuit in question, e.g. the original circuit from the particular mixer.
I certainly know, how a simple triac circuit should look like, but how should we know that it is the same circuit in the mixer?
There are plenty of circuits and far more then one way how an triac circuit could be designed.

[severach]

Re: Capacitor

Any chance you could fix that with Harbor Freight Item # 43060 Router Speed Control?

http://harborfreight.com/

I tried fixing a variable speed control once and I must not have got all the bad parts or the right replacement parts. It worked but lost most of its sensitivity across the dial range. It eventually burned out again. I just shorted out the internal components and ran the motor from one of these. Far cheaper than the replacement parts and super easy to replace.

[djrock]

Re: Capacitor

Hello, Sorry I forgot to mention I am fitting a new triac since testing it, it appears that has been taken out too. The guy I got the wrong caps off did say the traic could take out the caps. Thanks for the links I will have a good read of them.

Here are some photos of the circuit. I thought also I would draw a circuit diagram.


Thankyou

djrock

[severach]

Re: Capacitor

Your schematic is missing the blue wire from the motor to the 0.15uf cap. I was having trouble tracing power through the motor. The 3rd stripe on the 56r resistor looks brown to me which would make it a 560ohm resistor. The lower junction of resistor 56r and 0.47uf cap looks like it goes to more than nothing. I see a large contact down near the cooling blades that might be connected and has no obvious purpose and its height may be set by the spring loaded adjustment screws. The other contact is labeled "motor centre."

>The mixer (Kenwood Chef A901P) does still work but it's stuck on maximum speed

That tells me there's a speed control somewhere. I see the black dial but I don't see how it connects.

That motor has 6 contacts which seems like a lot to me. Seems like there might be something important besides a motor beyond that bundle of 4 wires.