Capacitor

[gonzo0815]

Re: Capacitor

The 0.047uF capacitor is for snubbing the induction currents from the motor. It`s value isn`t that critical.
The 0.15 capacitor is may be an auxiliary supply for the motor. So i would not change the value of the 0,15uF capacitor.

The 56R resistor is part of the snubber for the triac, thus i think 56R would be the right value for it. With 560R i am not sure, if it would be very effective in snubbing the spikes.
What kind of triac have you used as an replacement? I would try an BTA16-800BW.

[starfury1]

Re: Capacitor

Seems I wasn't very clear of what I was stating in the above post

Gonzo

Like I said I didn't know one way or the other,

I wasn't questioning what you had said

only that I had found mention of cap and trigger point in the formula
and thats why I said it as a possible in the post

I just provided the info for comment (post with schematic)

I also wasn't saying that the circuit would be the same as in the mixer either.
only provided in relation to formula so you would know what circuit the formula was relating to.

True there is more then one way to do things.

hope that clears it up a bit better

Cheers

[djrock]

Re: Capacitor

Hello,
---------------------------------------------------
severach
Resistor one is Green/Blue/Black/Gold. Resistor two is Red/Red/Brown/Gold
---------------------------------------------------
Gonzo0815

Kenwood's replacement triac is BT137-600F. I got a BT137-800 (I think it starts with bt137). The guy said it was a 600 but looking closely it's an 800, which I think is good since it can work with a higher voltage.
---------------------------------------------------
Replacement Caps
20% tolerance

0.047uf = 49nf
0.1uf = 96nf
0.22uf = 215nf
I tested each one and they seem fine.

If the 0.22uf is not a suitable replacement then I will use a 0.1uf and 0.047uf.

I found a small cap in both brush compartments. It's a 250vac RY 1n. I tested it with the multimeter I had with me and the reading was 3.5nf. Not sure if the multimeter reading is correct

---------------------------------------------------

I tested the old triac using the two tests on http://www.uoguelph.ca/~antoon/gadgets/triactst.htm and I think it's knackered but I wouldn't mind a second opinion.

Test 1

a. From T1 to T2.---133.2ohms
b. From T1 to the gate.---5.5ohms
c. From each terminal to chassis ground.---No ground connections.

Test 2

Attach the negative meter lead to T1 and the positive lead to T2.---5.9ohms

Now, using a screwdriver blade, create a momentary short between T2 and the gate. This brief contact should turn the triac "on", thus producing a meter reading of about 15 to 50 Ohms.--- Always on don't need to create a short

Next, disconnect one of the meter leads, then re-connect it. The meter should return a reading of infinity.----Still on.

The ohm readings might not be 100%.
---------------------------------------------------

I have attached more photos and a small video showing what happens when you turn the speed controller knob.


Thankyou

djrock

[severach]

Re: Capacitor

I hate to keep posting because all you need to do is replace parts willy nilly until it works. I keep trying to figure out how this thing works. I've come up with a diagram that should function but unfortunately I've had to suppose and gloss over a few things in the pictures.

I've decided that the "motor center" contact and the other contact which isn't the copper one we see in the pictures must be some sort of variable resistor adjusted by moving the electronics baseplate with the dial. We need a variable resistor connected to the gate and that's all I can see that connects to the gate.

I've decided that there must be a limit switch for the max position hidden behind the dial. This is what allows the mixer to operate at the max position when the electronics are open circuit and keeps the electronics safe at the highest load. Good dimmer switches also short bypass their TRIAC circuits at maximum load. At that limit switch the wire colors change so that the red/pink coming from the TRIAC isn't the same red/pink that goes into the motor brushes. If the mixer runs at max in all positions except off then the TRIAC is shorted and the limit switch might not exist. My limit switch idea is harmed by the fact that they use 4 wires where only 3 are required.

What do those 1pf caps connect to besides each other? Ground doesn't count since nothing else in the circuit connects to ground.

[djrock]

Re: Capacitor

Hello, Are you talking about the small orange/yellow cap with RY 1n on it? If so one side connects to the body of the motor and the other connects to the terminal with the red wire that the brush behind it touches.

Hopefully tomorrow I will be replacing the 2 caps, 2 resistors and the triac and we see if it sorts the speed problem.


Thankyou

djrock

[gonzo0815]

Re: Capacitor

The triac is obviously short, this is what i would say a typical failure mode of triacs.
The 1pF capacitors are to reduce the EMI from the motor and usually the case of the motor is included in this kind of EMI filter.
I have no doubt, that replacing the components will bring the circuit back to life.

[starfury1]

Re: Capacitor

I found a part supplier with photos but have yet to go through it
might help ID somethings for you serverach (not sure thought)

http://www.spares2go.co.uk/browse/A9.../m138/p588.htm

seems not all have photos
(site for ref only)

Also "thanks guys" for posting you got it further then I would have

Cheers

[starfury1]

Re: Capacitor

I found a small cap in both brush compartments. It's a 250vac RY 1n. I tested it with the multimeter I had with me and the reading was 3.5nf. Not sure if the multimeter reading is correct.

wouldn't the below be a 1 nF 100 pf ?

If you using a capacitance range on a multimeter the only reason that comes to mind is stray capacitance.

Does it have a pre zeroing thing?

guessing from the picture, if it was for EMI
(as Gonzo said and I agree)
wouldn't it go to ground the other end ?


Well I don't know on all 3 counts, so consider these more questions then answers





Keep us posted on how you go, be careful it is a mains circuit

Cheers

[djrock]

Re: Capacitor

Hello, No starfury1 it does not have a pre zeroing button.

I went to pick up the resistor and cap I ordered in from Maplin's warehouse to my local store and they sent the wrong cap.
I was not very pleased at having to make another trip when they get the right one in. So I managed to get them to send it through the post to me for free.

So it will be sometime next week before I start work on it.

I will keep you all posted on how it goes.

Thankyou

djrock

[djrock]

Re: Capacitor

Hello, Thankyou to Starfury1, Kikkoman, Gdement, Gonzo0815 and Severach for all your help!!

It now has all the speeds back! The motor at very low speeds has a bit of a funny noise (not sure if its normal) but disappear as you increase the speed. I think I can fix it.

djrock

[starfury1]

Re: Capacitor

the others really deserve the thanks they are more clued up on it them me.

not sure on the noise, motors I don't think like running slow, maybe the repairs just pushes a little too slow if you get what I mean

but no expert here.

I probably just not run it at slowest run it were it sounds right

but the other would I guess have more constructive input.

Good one thought glad to hear!

Cheers

[kc8adu]

Re: Capacitor

i would not worry about the sound.
my drill and dremel both sound odd at lower speeds.
just the nature of cheap triac controls.

[kiwitonita]

Re: Capacitor

Thanks to this helpful site and a couple of others I was able to fix a Kenwood Chef A901E by replacing the 0.1uF and 0.15uF capacitors and the 56 Ohm resistor. Have attached a few photos in case they help others.

[Krankshaft]

Re: Capacitor

This is why whenever I need to reduce the speed of a motor I just hook it to my variac.

Plain and simple no sine clipping or spurious emissions. Since the variac is a transformer if you were to look at the output on a scope you would see the amplitude of the sine wave decrease as you reduce the voltage.

If you look at the output from a triac on an oscilloscope (I did recently with an old dimmer) you will see the sine wave getting sliced and diced.

As for triac noise my Black and Decker drill motor whines at low speeds too same triac based design.

[derekjay]

Re: Capacitor

So was the result of all this that you could replace the 0.15uF capacitor on the A901E with an equivalent X2 rated 0.22uF capacitor?

http://cgi.ebay.com.au/Kenwood-Chef-...item33667cc541

Seems like you can get a 0.15uF Capacitor off ebay for this purpose. But the electronic stores in Sydney only stock 0.1uF or 0.22uF X2 capacitors.

[derekjay]

Re: Capacitor

So I replaced the 0.15uF capacitor with the 0.22uF capacitor and the machine runs fine. Although it is a little jittery at low speed (possibly caused by the change in capacitance, I don't know). Works well enough to make good pizza dough.

[PCBONEZ]

Re: Capacitor

I think all that cap does is keep switch and interlock contacts from burning when you make/break contact by 'softening' the spike.
.
If it's jittery at low speed it probably always was and you didn't notice before.
.

[mips]

Re: Capacitor

Got to love the internet, second time a google search brought me to this site and both times it has been very helpful.

I'm restoring the exact same food processor, this morning I turned it on and everything worked for a minute until the cap popped and let out lots of smoke. The cap was already cracked and bulging before I turned it on.

I managed to find a 0.22uF cap from a old TV circuit board and will try it out shortly.

The replacement cap I found has the following markings:
M - .22uF275V - ECQUL - 40/100/21 - GMF - MKT - DVE - 132400 - .C: - RU - SA - 250V - X2

Main reason I'm posting here is to upload circuit diagrams for the unit hoping it will help others in the future.


@ djrock & derekjay, the sound at low speed is normal, I had the same motor sound with the 0.15uF cap just before it popped

PS If anybody wants the full Kenwood Chef A901/7 service manual for this unit PM me and I'll email it to you. Very useful for when stripping the entire unit to individual pieces (including gearbox).


TAGS: Kenwood Chef A901 Circuit Diagram Schematic Capacitor 0.15uF

[budm]

Re: Capacitor

That cap is PANASONIC ECQUL series. I use them in the products I designed.
By the way, the caps in the 3rd picture: C1, C6, C7, C8, C9 must be safety cap X/Y type.
The .15 cap (X type) across the line is part of the EMI filter so the motor and the TRIAC will not inject the switching noise back into the line. The value of the cap was determine by the value of the two inductors and the frequency they want to reduce.
Post #28, that is the safety Y cap, one end in attached to the chassis, part of the EMI filter.
Post #16, the cap is not for snubber, it is part of the RC network for Phase firing of the TRIAC (same set up as a simple TRIAC control dimming circuits usin DIAC, r/c, and TRIAC: just Google "triac lamp dimmer circuit"), there is no subber network in that circuits, they should have R/C in series and put that across the TRIAC MT1 and MT2 terminal.

[mips]

Re: Capacitor

My motor is jerky at low rpm, however when I turn the mixer onto it's back or upside down the jerkyness goes away and it runs smoothly. Seeing the rotor has some free up and down play on it I can only think this might be related to the brushes?

Any ideas or suggestions?