Not sure if there is a known problem with this food processor or this was just a random blowout. Either way, I'm making a thread here, just in case it is the former. Luckily, this was another simple repair that only involved changing a TRIAC again. This time, it's a KitchenAid model KFP0924CU0 food processor.
Label:
https://www.badcaps.net/forum/attach...1&d=1501086923
Pressing the “Low”, “High”, and “Pusle” buttons did nothing other than the processor producing a relay click sound. Pressing the “OFF” button would de-energize the relay (another click sound). And that's it.
Tore it apart, and this is what it looked like inside:
https://www.badcaps.net/forum/attach...1&d=1501086923
Motor model information:
https://www.badcaps.net/forum/attach...1&d=1501086923
Top of the logic board (with old TRIAC already removed by me):
https://www.badcaps.net/forum/attach...1&d=1501086923
Bottom of the board (with old TRIAC removed and a jumper placed between T1 and T2 by me):
https://www.badcaps.net/forum/attach...1&d=1501086923
Original TRIAC was a BTA16-6CWG. It was open-circuited between terminals T1 and T2, but had a short circuit from Live (L) to Gate. So I started checking the driving circuit and found an open resistor. If I remember correctly, it was a 10 KOhm SMD. The driving transistor (TR2) was fine, however. So it looked like this food processor could be repaired.
Before purchasing any parts, however, I decided to check the rest of the circuit. It turns out that this food processor only uses the TRIAC for varying the speed on the motor (motor is a simple DC one, with permanent stator magnets). And in order to maintain the same speed, there is a magnetic tachometer on the motor's shaft that gives feedback to the main controller: a PIC16F716 microcontroller. (On that note, I find it amusing how nowadays even simple devices like a food processor use microcontrollers. ) The power to the TRIAC is switched ON and OFF by a relay, which is why I heard the clicking noises when I tried to run the food processor (the relay also shorts the motor's power wires when the food processor is OFF / not used, so that the motor blades will stock quickly and not move very much.) Thus, it looked like the microcontroller was also okay. Despite that, I decided to remove the old TRIAC and temporarily put a jumper across terminals T1 and T2 on the board to just test the motor. If everything was working okay, the food processor should run at full speed on both the “Low” and “High” settings. So I put the jumper on there and tested. Motor came running at full speed when the speed buttons were pressed, as expected… and turned OFF when the “Off button was pressed
Funny enough, I had the same exact TRIAC in my spare components box that I bought long time ago as a spare for fixing a busted cheap light dimmer from eBay (damaged by a “pro” technician way back when I worked in the small repair shop). So with that and a spare 10 KOhm SMD resistor from a busted CRT TV board, I got this food processor going quickly again.
Here is a picture with the new TRIAC installed:
https://www.badcaps.net/forum/attach...1&d=1501086923
And since this is badcaps.net, here is a shot of the capacitors inside this food processor :
https://www.badcaps.net/forum/attach...1&d=1501086923
As you cans see, they are some cheap, no-name brand. The logo looks like “LM” to me. Series is “GM”, and the caps are general purpose, rated for 85°C. From what I remember, they were used for smoothing power to the microcontroller. Power for the microcontroller is derived in the usual cheap manner: primary-connected film capacitor in series with a resistor in series with a Zener diode to primary neutral (ground). I imagine when the film cap goes leaky and cooks itself, this food processor will be coming my way again. But for now, it is fixed and working.
Label:
https://www.badcaps.net/forum/attach...1&d=1501086923
Pressing the “Low”, “High”, and “Pusle” buttons did nothing other than the processor producing a relay click sound. Pressing the “OFF” button would de-energize the relay (another click sound). And that's it.
Tore it apart, and this is what it looked like inside:
https://www.badcaps.net/forum/attach...1&d=1501086923
Motor model information:
https://www.badcaps.net/forum/attach...1&d=1501086923
Top of the logic board (with old TRIAC already removed by me):
https://www.badcaps.net/forum/attach...1&d=1501086923
Bottom of the board (with old TRIAC removed and a jumper placed between T1 and T2 by me):
https://www.badcaps.net/forum/attach...1&d=1501086923
Original TRIAC was a BTA16-6CWG. It was open-circuited between terminals T1 and T2, but had a short circuit from Live (L) to Gate. So I started checking the driving circuit and found an open resistor. If I remember correctly, it was a 10 KOhm SMD. The driving transistor (TR2) was fine, however. So it looked like this food processor could be repaired.
Before purchasing any parts, however, I decided to check the rest of the circuit. It turns out that this food processor only uses the TRIAC for varying the speed on the motor (motor is a simple DC one, with permanent stator magnets). And in order to maintain the same speed, there is a magnetic tachometer on the motor's shaft that gives feedback to the main controller: a PIC16F716 microcontroller. (On that note, I find it amusing how nowadays even simple devices like a food processor use microcontrollers. ) The power to the TRIAC is switched ON and OFF by a relay, which is why I heard the clicking noises when I tried to run the food processor (the relay also shorts the motor's power wires when the food processor is OFF / not used, so that the motor blades will stock quickly and not move very much.) Thus, it looked like the microcontroller was also okay. Despite that, I decided to remove the old TRIAC and temporarily put a jumper across terminals T1 and T2 on the board to just test the motor. If everything was working okay, the food processor should run at full speed on both the “Low” and “High” settings. So I put the jumper on there and tested. Motor came running at full speed when the speed buttons were pressed, as expected… and turned OFF when the “Off button was pressed
Funny enough, I had the same exact TRIAC in my spare components box that I bought long time ago as a spare for fixing a busted cheap light dimmer from eBay (damaged by a “pro” technician way back when I worked in the small repair shop). So with that and a spare 10 KOhm SMD resistor from a busted CRT TV board, I got this food processor going quickly again.
Here is a picture with the new TRIAC installed:
https://www.badcaps.net/forum/attach...1&d=1501086923
And since this is badcaps.net, here is a shot of the capacitors inside this food processor :
https://www.badcaps.net/forum/attach...1&d=1501086923
As you cans see, they are some cheap, no-name brand. The logo looks like “LM” to me. Series is “GM”, and the caps are general purpose, rated for 85°C. From what I remember, they were used for smoothing power to the microcontroller. Power for the microcontroller is derived in the usual cheap manner: primary-connected film capacitor in series with a resistor in series with a Zener diode to primary neutral (ground). I imagine when the film cap goes leaky and cooks itself, this food processor will be coming my way again. But for now, it is fixed and working.
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