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Kitchenaid Mixer Phase Control Board Problem

wdancer

Mar 12, 2010
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I have a Kitchenaid mixer that only runs on high speed. According to the service manual, this is caused by a faulty phase control board. Since I do not think I should have to spend $40 on a really simple PCB I decided to repair it. The schematic is in the service manual, but values and part numbers are not given. Here is what I was able to reverse engineer:

http://www.flickr.com/photos/85807139@N00/6344769414/

Q1 - STA06-600SW
Q2 - Unknown, suspected issue (Updated: ST MIcro DB3TG)
R1 - 120K 5%
R2 - 120K 5%
R3 - 100K 5%
R4 - 560 5%
R5 - 71.5K 1%
R6 - REMOVED FROM CIRCUIT
C1 - UNKNOWN VALUE
C2 - UNKNOWN VALUE

Q2 is what I am looking at to replace, since I already replaced Q1 and nothing changed. Q2 has a symbol I am not familiar with, it looks like a anode-anode dual zener diode, but I was thinking it may actually be a diac.

This kind of looks like a dimmer circuit used for lights, but it works by clipping the phases possibly? I am not very good with AC power circuits, so I need all the help I can get. I prefer my power with no zero crossings :)
 
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Resqueline

Jul 31, 2009
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It's a diac allright. It's the same circuit as in a dimmer except it has two R-C delay circuits for a more stable phase control which is needed for motors and transformers.
 

wdancer

Mar 12, 2010
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Thanks

Thanks, I was working on that assumption and i was thinking of a 32V 2A diac. Sound about right?
 

Resqueline

Jul 31, 2009
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Yes, that's what I had in mind too. That's the most common voltage and I'd be surprised if it didn't work. Some adjustment might be neccessary anyway.
I never noticed diac's being rated in Amp's before btw.. They're just to carry a short pulse, hard to define its peak level.
 

wdancer

Mar 12, 2010
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Well, my mixer works now. It was the diac. I still had to adjust set screws on the electro-mechanical governor plate that seems to adjust the phase pulsing somehow (I really did not want to tear into that). Thanks for the help. Hopefully, this thread will help anybody else trying to fix this.
 

bouldergla

Apr 27, 2012
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kitchenaid phase control board schematic

my phase control board has 2 film capacitors: 0.1 uF and 0.022uF

when i pulled the triac out, the caps came with it (they were glued together)

i got replacement caps, but i am not sure which is which (i.e. which value would be closer to the triac). kitchenaid schematic labels C1 as connected across blue and black wires and C2 connected to R4 and Diac

i know there are different versions of the board, but in mine the caps were rectangular and parallel to the triac face (and all 3 glued together). if anyone has the board with numbers on the caps or can tell me just based on circuit principles which is which, i would appreciate it
 

davenn

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Sep 5, 2009
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without seeing how the board was originally or seeing a circuit diagram its difficult to say
you know for next time always make notes and or photos before removing parts

Tis a bit unfortunate that that cct inthe link above doesnt give part values

Dave
 
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bouldergla

Apr 27, 2012
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yes, i wasn't expecting the caps to be glued to the triac (the leads of the cap pulled out of the body

then my wife didn't recognize the small rectangular boxes as something of interest so they got thrown away

a bit of murphy's lay going here

i am thinking the .022uF goes nearer the triac but would like other opinions or someone who has knowledge of this circuit
 

wdancer

Mar 12, 2010
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I didn't pull the caps to check the values since they were still working (it wasn't broken, so I wasn't fixing it). I'll check my phase board this weekend to see if there are any visible values on them.

I would assume that the smaller value would be C2 to help with noise, while the larger value would be C1 as part of an RC time constant.

Also, remember to put some good thermal paste on the back of the triac. I believe that heat dissipation may have played a part in the demise of my circuit. Use a hair dryer or heatgun (on low) and a pick to soften and remove the hot glue and conformal coating next time. Makes it a lot easier.
 

bouldergla

Apr 27, 2012
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wdancer, thanks

i did think of 1 other point of data

the 0.1uF was rated 100V, the 0.022uF was rated 400V

i haven't been able to wrap my head around the circuit enough to see if this is a clue, but if it is, then i would think C1 is more "exposed" and the voltages across C2 would be more constrained

but it might be that .022 just came in 400V

my caps were rectangular boxes with a string of numbers on them that actually i did decode (something like 10104100 (e.g. 10 x 10**4 10% 100V)).

thanks!
 

wdancer

Mar 12, 2010
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Yeah, the wife throwing things away is why I started to do what I do at work; writing down component reference designators and values along with taping the bad components to my paperwork. It is a lot less likely to just get thrown away if it looks like something that is actually organized ;)

I agree with the larger voltage rating being on the motor side. The inductive load being generated as the motor is slowing after you turn it off is probably pretty decent.

As I was Googling to look for more example circuits (triac diac ac motor control), I saw most had matched caps, but others had a larger value as the snubber and others had a smaller value. Here is one link that gives a decent description of what is going on.
 

bouldergla

Apr 27, 2012
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update ...

i found another mixer that i borrowed from a friend.

so you can look at the schematic of the board as wdancer posted and his values for resistors

here are his missing values:

C1 is the 0.1 uF
C2 is 0.022 uF

as a side note, 0.1 uF is sometimes listed printed with the numbers 10 and 4 meaning 10 times 10*4 or 10 times 10000 pF or 100,000 pF
that means .022uF might be printed with the numbers 22 and 3 meaning 22 times 10*3 or 22,000 pF

i replaced the triac with BTA16-600 (16 amp triac; yes overkill considering you are replacing a 6 amp one, but no downside to using a higher current rating and potentially a little more tolerant of potential overheating). put thermal compound on it to the heatsink and on the back of the heatsink to the mixer housing

i think more than 90% of the failures are the triac; when i took my triac out i damaged the capacitors

i replaced C2 with the same 400V rating
i replaced C1 also with a 400V rated (original was 100V rated); new technologies offer 400V in a size that fits; again no downside to upgrading

WORKS GREAT ! Thanks for the forum.
 
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TomTinker558

Feb 7, 2014
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I just wanted to chime in and say thanks for the great thread....it solved my non-starting KitchenAid Pro 600 Series mixer (Model # KP26M1XER --- 6-Quart --- Purchased in 2012).

The culprit was a defective Triac p/n BTB10-600BW (it is a TRIAC, *not* a Diac like mentioned elsewhere in this thread).

I simply replaced it with a new Triac from STMicroelectronics, part number BTB24-800BW (non-insulated; 25 A current; 800 Volts; 50 mA sensitivity; Snubberless). The new part cost me roughly $2.00 from Mouser Electronics. I of course utilized thermal compound on the back of the triac as it compressed on the heat sync. Also, I used a nice steel pop-rivit to affix the triac to the heat sync & circuit board.

The new Triac is far better and the current rating is substantially higher than the original Triac. (old Triac rated at 10 A current; 600 Volts)

----

As an aside, note that there are multiple speed control circuit boards designs, based on the particular year the unit was manufactured & model in question. For me, the Pro 600 series (model #KP26M1X..) utilized KitchenAid circuit board part #9706650 (this p/n replaces the following older part numbers: 9707220, 9707172). It is my understanding that the same speed control board also is utilized in the following 6-quart mixers: KP26, KT26, KD26, and KB26.

----

Thank you again for your help and I couldn't have solved the problem without all your great tips & info.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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The culprit was a defective Triac p/n BTB10-600BW (it is a TRIAC, *not* a Diac like mentioned elsewhere in this thread).

The original board had a diac as well as a triac on it.

Glad you got yours fixed, and good choice to go with a meatier triac.
 

cdhunter

Aug 30, 2014
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Aug 30, 2014
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I know this thread is old, but it has been a great help. I was hoping the original poster would be able to post what kind of mixer he was fixing
 

bouldergla

Apr 27, 2012
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i'm not sure exactly which model was wdancer but mine was the k5 if i remember correctly.
as far as i know all of the kitchenaid mixers use this same scheme but the boards have varied somewhat over time
 

cdhunter

Aug 30, 2014
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Aug 30, 2014
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Just a follow up replaced both the triac and diac, and to quote dr Frankenstein " it's alive ". Just want to say thanks guys this thread was a huge help. And for others finding this thread my mixer was a artisan, and I got my arts through Digi key
 

Axel

Sep 18, 2016
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Sep 18, 2016
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I have a strange problem with my KSM150PS which have the same phase board.

Speed 1 to 4 have the same speed. When start on "stir" motor start about 100rpm and goes in 10 sec. to about 120rpm. Governor and Control plate work as well. The Governor want to break the circuit and press on control plate. I think it must be the phase board.

On my first test i have disconnect the blue and red/white wires from control plate. So the motor must start on slowest speed but it goes to 100rpm.

The next try was change triac and diac on phase board. Same result.

Then i change the caps on phase board. Same result.

Then i change all resistors on phase board. Same result. :mad:

The measured motor power was 40.6V

Any ideas?

The resistor R5 on my phase board has 62k 1%. Can someone confirm that?
 
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Toolkitguy

Jul 30, 2012
2
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Jul 30, 2012
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I have a Kitchenaid mixer that only runs on high speed. According to the service manual, this is caused by a faulty phase control board. Since I do not think I should have to spend $40 on a really simple PCB I decided to repair it. The schematic is in the service manual, but values and part numbers are not given. Here is what I was able to reverse engineer:

http://www.flickr.com/photos/85807139@N00/6344769414/

Q1 - STA06-600SW
Q2 - Unknown, suspected issue (Updated: ST MIcro DB3TG)
R1 - 120K 5%
R2 - 120K 5%
R3 - 100K 5%
R4 - 560 5%
R5 - 71.5K 1%
R6 - REMOVED FROM CIRCUIT
C1 - UNKNOWN VALUE
C2 - UNKNOWN VALUE

Q2 is what I am looking at to replace, since I already replaced Q1 and nothing changed. Q2 has a symbol I am not familiar with, it looks like a anode-anode dual zener diode, but I was thinking it may actually be a diac.

This kind of looks like a dimmer circuit used for lights, but it works by clipping the phases possibly? I am not very good with AC power circuits, so I need all the help I can get. I prefer my power with no zero crossings :)
$14 on eBay. Cost of parts with shipping will be about the same. Plus no soldering.
 
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