Anyone have experience with Cuisinart CYM-100 Automatic Cool

This will be my weekend project but before I tear into it, I wonder if anyone has any experience with these or knows of a schematic? This is the third one I've had. First one quit cooling, the second one and this one stopped heating.
Given my experience with failure rate, these things seem poorly designed.

I am guessing it contains Peltier module and if that is true, I suspect the module may be dead or the drive circuity may be the culprit.
Any insight from anyone having experience with this is appreciated.
J

 

On Friday, April 17, 2020 at 10:21:49 AM UTC-4, jjhu...@gmail.com wrote:

Given my experience with failure rate, these things seem poorly designed.

The design could be fine, but the execution could be the problem.

Did you keep the old ones by any chance?

 

On Friday, April 17, 2020 at 12:56:51 PM UTC-4, str0...@aol.com wrote:

On Friday, April 17, 2020 at 10:21:49 AM UTC-4, jjhu...@gmail.com wrote:

Given my experience with failure rate, these things seem poorly designed.



The design could be fine, but the execution could be the problem.

Did you keep the old ones by any chance?

Good point - yes bad implementation of a design. (like having a cheap fan blow across the Peltier (if it uses one) or, badly implemented airflow passages after all the components were shoe-horned into the package.)

Did not keep the old ones - both were warranty replacements with a $25 surcharge for replacement. I figured it was worth the $ and not my time. Now, since this one went belly up (and there seems to be a lot of similar failures posted in user feedback) I figure I need to get in and *really* fix this thing - if my spouse wasn't so enamored with it, I'd dig out the 15 yo Salton one to use.

 

Following up on my repair effort, I'll document what I found in case anyone going down this road stumbles on this writeup.

In short the unit uses a Peltier module heat pump to both heat and cool the yogurt container. The Peltier module was bad in my unit - gave a constant ~30K ohms reading, connected it to a 12vdc battery source, no heat what so ever.
The module is a TEC1-12705.
To my surprise none of the usual electron parts houses have them (Mouser, Digikey, avnet, allied, newark, etc.) Amazon has them ranging in price from $6 to $10 from varying sources and from what I see in the reviews, all parts are of questionable quality. To my surprise, they are available through Walmart!
Not sure where to get the OEM part - suggestions? pointers appreciated.

Description of the unit, it contains:
1) 5 VDC 6A smps, which feeds a...
2) a 2"x3" micro based control module that contains connections for: the Peltier module, a rtd/thermister temp sensor, power supply input.
3) the heat/cool stack composed of 1.25" aluminum heat block encased in styrofoam, the peltier module, a massive Al finned heatsink (5"x 2.5") and a 3" fan bolted to the finned heatsink.

Getting the unit apart is a little tricky because it has 4 plastic fingers that lock the bottom half of the unit to the top half - need to simultaneously unlock all four tabs then separate the top and bottom.

Couldn't see any obvious design or implementation screwups, although I question why there is a 1.25" thick piece of aluminum between the Peltier module and the bottom of the yogurt container. I'll need to do some heat transfer calcs to see if they are controlling the module correctly and take some temp measurements to infer their desired (required) heating and cooling temps.

From what I could tell on the scope the output to the Peltier module was fairly smooth DC voltage that is (my guess) a LPF PWM output to a power transistor (MOSFET?) from the microcontroller The markings on the chip were unreadable due to some clear coat that was put on the chip. A lot of speculation here since I could not read a lot of the component markings. My googlefu failed to turn up anything about the components, although the PS looks like it is an off the shelf module from somewhere.


Next step is to get the replacement Peltier module, perhaps upgrade the thermal silicon grease, and reassemble.
J

 

[John-Del]

On Sunday, April 19, 2020 at 4:43:08 PM UTC-4, jjhu...@gmail.com wrote:

Following up on my repair effort, I'll document what I found in case anyone going down this road stumbles on this writeup.

In short the unit uses a Peltier module heat pump to both heat and cool the yogurt container. The Peltier module was bad in my unit - gave a constant ~30K ohms reading, connected it to a 12vdc battery source, no heat what so ever.
The module is a TEC1-12705.
To my surprise none of the usual electron parts houses have them (Mouser, Digikey, avnet, allied, newark, etc.) Amazon has them ranging in price from $6 to $10 from varying sources and from what I see in the reviews, all parts are of questionable quality. To my surprise, they are available through Walmart!
Not sure where to get the OEM part - suggestions? pointers appreciated.

Walmart is a poor man's Amazon. Many of the things sold on Walmart's online site are deliverd from someone's basement, and I don't know if Walmart would offer the same protections as Amazon, as good or as bad as that might be.

 

[Allodoxaphobia]

On Mon, 20 Apr 2020 04:46:45 -0700 (PDT), John-Del wrote:

On Sunday, April 19, 2020 at 4:43:08 PM UTC-4, jjhu...@gmail.com wrote:
Following up on my repair effort, I'll document what I found in case anyone going down this road stumbles on this writeup.

In short the unit uses a Peltier module heat pump to both heat and cool the yogurt container. The Peltier module was bad in my unit - gave a constant ~30K ohms reading, connected it to a 12vdc battery source, no heat what so ever.
The module is a TEC1-12705.
To my surprise none of the usual electron parts houses have them (Mouser, Digikey, avnet, allied, newark, etc.) Amazon has them ranging in price from $6 to $10 from varying sources and from what I see in the reviews, all parts are of questionable quality. To my surprise, they are available through Walmart!
Not sure where to get the OEM part - suggestions? pointers appreciated.

Walmart is a poor man's Amazon. Many of the things sold on Walmart's online site are deliverd from someone's basement, and I don't know if Walmart would offer the same protections as Amazon, as good or as bad as that might be.

Walmart == Made In China Store

Even those who lower
their expectations
are often disappointed.

 

On Sunday, April 19, 2020 at 4:43:08 PM UTC-4, jjhu...@gmail.com wrote:

Following up on my repair effort, I'll document what I found in case anyone going down this road stumbles on this writeup.

In short the unit uses a Peltier module heat pump to both heat and cool the yogurt container. The Peltier module was bad in my unit - gave a constant ~30K ohms reading, connected it to a 12vdc battery source, no heat what so ever.
The module is a TEC1-12705.
To my surprise none of the usual electron parts houses have them (Mouser, Digikey, avnet, allied, newark, etc.) Amazon has them ranging in price from $6 to $10 from varying sources and from what I see in the reviews, all parts are of questionable quality. To my surprise, they are available through Walmart!
Not sure where to get the OEM part - suggestions? pointers appreciated.

Description of the unit, it contains:
1) 5 VDC 6A smps, which feeds a...
2) a 2"x3" micro based control module that contains connections for: the Peltier module, a rtd/thermister temp sensor, power supply input.
3) the heat/cool stack composed of 1.25" aluminum heat block encased in styrofoam, the peltier module, a massive Al finned heatsink (5"x 2.5") and a 3" fan bolted to the finned heatsink.

Getting the unit apart is a little tricky because it has 4 plastic fingers that lock the bottom half of the unit to the top half - need to simultaneously unlock all four tabs then separate the top and bottom.

Couldn't see any obvious design or implementation screwups, although I question why there is a 1.25" thick piece of aluminum between the Peltier module and the bottom of the yogurt container. I'll need to do some heat transfer calcs to see if they are controlling the module correctly and take some temp measurements to infer their desired (required) heating and cooling temps.

From what I could tell on the scope the output to the Peltier module was fairly smooth DC voltage that is (my guess) a LPF PWM output to a power transistor (MOSFET?) from the microcontroller The markings on the chip were unreadable due to some clear coat that was put on the chip. A lot of speculation here since I could not read a lot of the component markings. My googlefu failed to turn up anything about the components, although the PS looks like it is an off the shelf module from somewhere.


Next step is to get the replacement Peltier module, perhaps upgrade the thermal silicon grease, and reassemble.
J

Last follow-up on my repair.
The Peltier module I got from Amazon seller did not conform to the general rule that the 'hot side' is the side that has the p/n printed on it. Mine was opposite, which I did not find out until I had the unit reassembled and tried it. The module broke when I tried to remove it - the thermal grease made it very difficult to remove. Ordered a second module.
When I got the replacement, I tried it before putting the thermal grease on it and assembling it.
I connected the red wire of the Peltier module to the '+V out' on the controller board, and the black wire of the module to the '-V out' on the controller. Powered up the unit and started a cycle. The first thing that is suppose to happen is a heating phase (default time of 8 hrs but is configurable) followed by a cooling phase. I started a cycle, felt the module for the heat side, and then mounted that head side against the thermal plate on the 'container side' of the unit. The voltage sent to the Peltier module is 12 VDC. A quick check of the control module is to start a cycle and measure the voltage. at the +Vout and -Vout pins.

Once the heating/cooling side was determined, I reassembled the unit. A word of caution: the massive heat sink in the 'bottom half' of the unit is held in by four machine screws. ( this heat sink comes into play when the unit goes to a cooling phase and changes polarity on the Peltier module).
The machine screws had silicon rubber spread on top of them, presumably to deter any repair. You will have to scrape it out of the fillips screw heads to get a bite with a screw driver. Once out, the rest can be removed with a wire brush.
The heat sink has rubber spacers on each end of the heat sink. Do not remove these. When reassembling, do not overtighten the screws when installing the heat sink. Try to remember how 'loose' they were when you removed them and tighten them to about the same level. I made mine snug to the point that there was just a little resistance from the rubber spacers. If the screws are overtightened, it could crack/damage the module. A good application of thermal grease here is important.

I got the replacements from seller on Amazon and prices range from ~$2/part to ~12/part. Comments for any of the parts ranged from good to junk...no matter what the price. I paid $6. I called Laird who makes TEC modules and they have a cross that sells for $32 at mouser. I decided to try the $6 part and see what happens. If it dies, I may go for the expensive one but Cuisenart will replace the unit for $25+10 ship so it probably isn't worth the effort and cost. YMMV.
I didn't see any obvious design or implementation flubs (that I could easily correct). I do question why the metal block to the yogurt well was over 1 inch long.

Hope this info helps someone.
J