I just picked this up for $85 plugged it in for 24 hours and neither zone is cooling. The front display comes on and I can set the thermostats independently, but no joy.

I can hear a very low hum when plugged in, but neither fans run (back cover removed). I can't tell if the 2 boards are the FX-101, FX-101B or FX-102, but the boards are made by Hanny with the following model (maybe?) C-7754C. Both fans spin freely by hand, there are no LEDs on either board.

I understand that MOST problems are due to the C8 cap, but could it be that both are out? I suppose it's a possibility since both reside in the fridge and have been subjected to the same conditions. I just order new caps and star there. Fingers crossed. I will report back.

 

Looks like there are two switch-mode PSUs boards, you can check if the boards are getting a mains supply on the Black and White wires input, and if there is a DC supply on the two Large black Capacitors . The circuit is powered by the 16pin TL494 chip supply pins are 12/7.

 

Sounds like something common to both PSU. Check for AC input to both boards as Dave says.

 

Thank you for the feedback. I will check the inputs as recommended, but would the front display still work if there were no mains supply? The fridge is not completely dead.

 

Looks like there are two switch-mode PSUs boards, you can check if the boards are getting a mains supply on the Black and White wires input, and if there is a DC supply on the two Large black Capacitors . The circuit is powered by the 16pin TL494 chip supply pins are 12/7.

I'm hoping I did that right, so I measured the voltage at pins 7/12 on both boards and am getting 1.12 Volts and 1.62 Volts respectively, and 0 Volts and 0.5 Volts on the two large caps of one of the boards.

I received the C8 caps but have not replaced them yet.

 

If you're not getting anything on the large capacitors then there's no mains input, check for AC on the Black and White wires coming in.
Check the fuse and the green thermal resistor.

 

If you're not getting anything on the large capacitors then there's no mains input, check for AC on the Black and White wires coming in.
Check the fuse and the green thermal resistor.

View attachment 303669

I have already checked the mains input on the black and white wires, and there is line voltage there. As I said at the top of the post, the front display of the fridge is working and so is the interior light, and I can change the temperature setting as well. There is voltage coming to both boards.

I must have measured voltage at the large caps wrong. As silly as this might sound, but how am I measuring voltage there? Should I be getting 12 volts DC? Am I measuring across the two terminals at the caps?

I need to check voltage a the fans and Peltiers and work my way back. It's obvious that there is no voltage or perhaps low voltage even, otherwise the fridge would be working, I just don't know what to look for. Strangely (or coincidentally) enough both boards aren't working, so they both are subject to the main issue.

 

The voltage on the Capacitors will be around 200V DC , check the fuses and the green Resistor as they might be blown.

The circuit is a switch-mode type, it pulses the mains voltage to produce low voltage DC all controlled by the 16pin chip. These are a nightmare to repair.

 

The voltage on the Capacitors will be around 200V DC , check the fuses and the green Resistor as they might be blown.

The circuit is a switch-mode type, it pulses the mains voltage to produce low voltage DC all controlled by the 16pin chip. These are a nightmare to repair.

Both the fuse and resistor checkout fine. I'm getting 6 ohms in-circuit on the resistor.

I also remeasured the 2 large caps and I'm actually getting 161 volts on both.

 

Here is a sample circuit diagram of what these are, your circuit board is similar to this. It will help you to follow the mains input side.

 

Both the fuse and resistor checkout fine. I'm getting 6 ohms in-circuit on the resistor.

I also remeasured the 2 large caps and I'm actually getting 161 volts on both.

I also just replaced the C8 cap on the same board, but unfortunately, no joy!

 

Here is a sample circuit diagram of what these are, your circuit board is similar to this. It will help you to follow the mains input side.

View attachment 303709

Thank you for attaching the schematics. My knowledge of circuits is unfortunately very limited. I certainly understand what each compnent does individually, and understand what a rectifier bridge is, for example, but putting it altogether is where I run into problems. If my next guided steps do not result in fixing this, I am considering replacing both boards with the following 12V, 30A, 360W PS: https://www.amazon.com/dp/B06XJVYDD...SK3Z4769R&ref_=list_c_wl_lv_ov_lig_dp_it&th=1

 

The ones that you have found on Amazon, are only giving out 12V i think the cooler boards give out other voltages as well?

 

The ones that you have found on Amazon, are only giving out 12V i think the cooler boards give out other voltages as well?

You mean to the pelletiers? Or the actual circuit boards?

 

You mean to the pelletiers? Or the actual circuit boards?

Just looking at the boards they have four connections on the output side , are they all 12 V supplies?

 

Just looking at the boards they have four connections on the output side , are they all 12 V supplies?

I think so. There should be two for the fans, one fan on the pelletier and one inside the fridge (pushing/pulling air), another output for the pelletier itself, and one for the temp display and LED inside the fridge.

 

I think so. There should be two for the fans, one fan on the pelletier and one inside the fridge (pushing/pulling air), another output for the pelletier itself, and one for the temp display and LED inside the fridge.

Are you able to measure 12VDC at all of those points?

 

I think so. There should be two for the fans, one fan on the pelletier and one inside the fridge (pushing/pulling air), another output for the pelletier itself, and one for the temp display and LED inside the fridge.

If there is no 12V output then the oscillator circuit isn't working , ( ref post#10) Q1and Q2 and the components around these two transistors, especially the two caps, check these out.
Once they are working the chip takes over and controls the output voltage.

 

If there is no 12V output then the oscillator circuit isn't working , ( ref post#10) Q1and Q2 and the components around these two transistors, especially the two caps, check these out.
Once they are working the chip takes over and controls the output voltage.

View attachment 303740

For me to test the transistors I would have to remove them from the boards which I don't want to do quite yet, reason being I don't think the issue is in the supply of power (12 volts). While the pelletiers and fans aren't working now, the temperature display and internal blue LED are, which leads me to my conclusion above. We are also talking about a dual zone fridge with 2 identical boards. What are the chances that the same exact components would end up being fried on both boards?
Quite possible, but since I don't know the history of this fridge, we'll never know. Keep in mind that the fuses and resistors I was asked to test in post #8 are intact, ahd there been a surge of some sort wouldn't have those fried?

Whatever is causing the absence of voltage to the fans and pelletiers has to be common to both boards. We know that the thermistors are what triggers those boards, and there are 2 of them here, one for each zone, and both are working fine.

I was always taught to look for the simpler things when diagnosing a problem before diving into the minutia. Is there something we're missing?

 

The display board must be getting power from somewhere.
Do the temperature displays appear to be show correct temperature?

Presumably, the display board (or controller) has to send control signals to the PSU in order to enable power to the fan and TEC. That is where you have to look at next.

I just fixed someone’s Miele dual zone wine cooler. The problem was user error in that the user did not know how to adjust the settings. Just saying.