Need help repairing thermoelectric cooler

Thread Starter

Condeellum

Joined Sep 22, 2023
6
Hi all!
Someone passed me a Husky HUS-CN9 drinks cooler, saying, "It works, but I have no space for it." However, I wouldn't be writing here if that were true.
Upon opening it up, I discovered some residue on the circuit board, and there are two burnt spots on the back. Thinking I could fix it, I purchased an FX-102 PCB121110K1 board and swapped it in, making sure to connect everything as it was labeled on the original board (GCH-A11). However, the cooler still doesn't work.

Here's how I connected the new board:
- NTC to NTC1
- FAN (outer fans) to FAN1
- A 3-pin connector to NTC2 (3-pin socket)
- TEC (red and black wires) connected to P1 and P2 output pins on the new board

379667215_6622190354515643_6452588951831233837.jpg
( the two FAN plugs should be swapped, below you will find a picture from the seller with the correct wiring but when I swapped does not seem to change in operation. Originally the ground and +8V wires from the NTC2 socket powers the inner fan.)

The current issues I'm encountering with the board are as follows:
- Upon powering up, only the red LED remains continuously lit, while the green LED doesn't illuminate.
- Both inside and outside fans are spinning slowly.
- After running for an extended period, there is only a 2°C temperature difference, with the inside remaining cooler.
- Adjusting the thermostat to high or low settings doesn't appear to affect the board's operation.

For diagnostic purposes, I made several measurements:
- When nothing is attached to the board, I measured (+)8V in all sockets (except NTC1, which measured (-)8V).
- When I attached the TEC, the voltage on the output pins dropped to approximately 2.6-2.8V, drawing 0-1.4 Amps (fluctuating rapidly).
- The voltage also dropped on NTC1 (to around (-)2.8V), and NTC2 measured (+)5V.
- I powered the TEC using a 12V 10A power supply, and it drew around 3.6-3.8A, with the temperature slowly increasing on the outer heatsink.

I also measured the resistance of some components:
- The TEC size is 50*50*4.9mm and the resistance is 10-11 ohms, which appears within an acceptable range. However, I don't know the part number, as the TEC is binded to the outer heat sink and I could not remove it.
- The thermostat module: The potentiometer ranged from 10 ohms to 4.5k ohms (low to high settings), and the NTC measured 9.27k ohms at room temperature (for the 10k ohm 25°C thermistor). The entire module had a resistance range of 13.6k ohms to 18.3k ohms (low to high settings).

The module in more detail:
- It has a 3-pin socket. Two wires come from NTC1, and one wire comes from NTC2.
- from NTC1 has two wires connected to the thermostat module's 3-wire connector. The ground wire is attached to a 4.8K resistor, followed by a potentiometer and a parallel 10K resistor (I can't see properly), and then the 10k NTC, with the circuit returning to NTC1.
- from NTC2 (3-pin socket) comes one wire and connects to the thermostat's 3-wire plug, goes through an on/off switch, capacitor, and resistor (750Ω), and then reconnects to the previous ground circuit involving the 4.8K resistor.
- An LED is also connected to the capacitor.

383234577_7024155750937548_4617453575958168612_n.jpg

382336404_255297597498972_7395521063022407358_n.jpg

384071906_1028933678137322_7039186125546818457_n.jpg

After researching on this forum, I found that many suggest swapping the capacitors, but since it's a new board (hopefully), I first contacted the seller for assistance. I described the issue and received the answer that if I short the ground and the middle pin on the NTC2 connector, I can test the board, and it should switch to 12V. So, I did that, and the green LED lit up continuously, and the TEC also started working (temp noticeably rises, measured by temp probe).

However, it still doesn't work with my temperature control module. I had some further questions, and I received the question: "May I ask if the positive and negative levels of your refrigeration chip have been reversed?" But I have no idea what that means. I requested more information, I also sent some pictures of the old board, and the response I received was the following picture and "Your old board is different from ours and may not be good."
1696753846802.png

Here on the forum I found in a previous post and checked the MP-12 schematic with the temperature control module and I found that my module is different, kind of back-warded. So, I asked about what I should attach to the pins and if I could get a schematic for the temperature control module for rebuilding purposes, but I haven't received it.

If anybody has experience with the FX-102 PCB121110K1 board, I would greatly appreciate some help with the wiring, or if necessary, I'm happy to rebuild the temperature control module.

I am also interested in what is the ideal (50mm*50mm) TEC for this FX-102 board.
 

MrChips

Joined Oct 2, 2009
30,518
Welcome to AAC!

If your cooler does not cool, the first thing to check is the DC voltage going to the Peltier TEC element. If you have already tested the TEC with a bench power supply, 4A @ 12V is 48W. You should feel the TEC getting cold on the cold side almost instantly and hot on the hot side. I am going to hazard a guess that the TEC element is bad.
 

Dodgydave

Joined Jun 22, 2012
11,255
Check the voltage across the chip pins 7 and 12 it should be around 16V, this should tell you if the power supply is working.

Here is a circuit diagram posted in a previous thread by @MrChips , it looks like yours is the same thing.. the two leds are in the diagram.
IMG_20231008_171557.jpg1696260541475.png
 

Thread Starter

Condeellum

Joined Sep 22, 2023
6
Hi,
I appreciate your help in moving my post to the right section of the forum.
I tested my TEC with a 12V 10A power supply, and it drew approximately 3.6-3.8A. When I shorted the ground (GND) pin and the middle pin in the NTC2 connector, the green LED lit up. At this point, there was 12.6V on the TEC pins, and it started working as expected. The cold side became cold, and the warm side warmed up.

I also measured the voltage on pins 7 and 12, and I found 16.6V and 17.48V, when I shorted the GND and middle pin.

I came across the Portuguese article that references the NTC1 connector as the outer temperature sensor. However, in my current setup, I do not have an outer temperature sensor. Should I have one for my setup, or can I proceed without it?

If I decide to build a temperature control module similar according to the Portuguese article, would it work seamlessly with my board? The schematic in the article seems promising, but I want to make sure it's compatible with my setup.

Thank you in advance for any insights and advice you can provide.
 

Thread Starter

Condeellum

Joined Sep 22, 2023
6
Do you mean something like this?
1696951345592.png
If yes, then how do I wire this? I have 12V at NTC2 if I short it.
And what goes in the NTC1?
 

Thread Starter

Condeellum

Joined Sep 22, 2023
6
Okay, thanks for this. The 7K (±4K tolerance) switching temperature is not too high?
Does it mean if I set the temp to 10C, it will switch off at 10C and switch on at 17C?
I'd like to use this cooler for storing mushroom culture plates and would be great if the temp is consistent and there is no such a huge temp fluctuation. The temp fluctuation influence the growth speed and the longevity of the storage.
I'm happy to buy the KTS011, if it meets with my requirements but I'm also happy to rebuild the temp module and buy an extra NTC for the TEC if I get some instruction.
 

Thread Starter

Condeellum

Joined Sep 22, 2023
6
Can anybody help me? I still could not find solution for the temp control.
The above mentioned KST011 with 7K (±4K tolerance) switching temperature seams huge temp fluctuation for my mycology needs.
If there is another option, I'm opened for it.
I re-read this Portuguese article. That board seems similar like mine and I'm happy to follow it but I have questions.
1. What type of NTC do I need for the NTC1 connector? Which should measure the outer temp.
2. Will work if I rebuild the "Internal panel, with potentiometer" according to the provided schematic? Which connect to NTC2 (three pin connector)
 
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