Wine and Beverage Cooler Control Board Repair Attempt

[R_J]

The microprocessor has a reset, in this case it may be POR not an external reset so it is likely pin 7 is configured for something else

The MC96F6432S has five types of reset sources. The following is the reset sources.
− External RESETB
− Power ON RESET (POR)
− WDT Overflow Reset (In the case of WDTEN = `1`)
− Low Voltage Reset (In the case of LVREN = `0 `)

[stj]

reset for the microcontroller?

[R_J]

Not sure what EC14 is for exactly, but it seems to be for some time delay. its negative is connected to ground and its positive connects to R41 (5kΩ) and D15 cathode and the other end of R41 connects to +5 volts, D15 anode goes to pin 20 of IC1
So 5 volts charges EC14 via a 2meg resistor and the anode side of the diode connects to the 5v via R42 (30kΩ)

[KYBOSH]

EC11 is the output filter for the U1 5 volt regulator, it better not have more than 5 volts on it. I would need a clearer picture of the board to see the actual traces to trace the function of EC14 but it is likely on a vcc supply line for something that is turned off at the moment

You could check the voltage on IC1 pin7 this is the microprocessors reset pin.It looks like the voltage should be about 1.4v

The Dude abides...

[R_J]

EC11 is the output filter for the U1 5 volt regulator, it better not have more than 5 volts on it. I would need a clearer picture of the board to see the actual traces to trace the function of EC14 but it is likely on a vcc supply line for something that is turned off at the moment

You could check the voltage on IC1 pin7 this is the microprocessors reset pin.It looks like the voltage should be about 1.4v

a closer look at IC2 and I think it is the same as IC3? instead of driving the relays it drives the led strings L5, L6, L1

[KYBOSH]

EC13 is across F2 and +12v if the fan is not turned on, no voltage. EC12 is across F1 and +12v same as F2 not sure about Ec14 but it might be associated with IC2 which seems to be a led controller

I wouldn't be surprised by this. Not sure if the controller would turn on the fan if the compressor was not working/on.

EC11 and EC14 never get more than 5v which is not even enough to light up the LEDs which have a forward voltage of almost 7v.

[R_J]

EC13 is across F2 and +12v if the fan is not turned on, no voltage. EC12 is across F1 and +12v same as F2 not sure about Ec14 but it might be associated with IC2 which seems to be a led controller

[KYBOSH]

I was looking at the Edgestar brand which is slightly different

Yes, these things are ridiculously expensive for what they are (a refrigerator albeit quite fancy!).
Im going to probe around a bit (small smd diodes, transistors, etc) as Im wondingering why Im not seeing better/higher voltages on the smaller caps but I doubt I'll spend much more time on this as I cant think of anything else to do. Thanks to you guys for all your help and ideas. I learned a lot and REALLY enjoy sharpening my chops with this troubleshooting exercises. Might not pay off today but the confidence and understanding you build will certainly payoff on the next one(s).

[R_J]

I was looking at the Edgestar brand which is slightly different

[KYBOSH]

The power supply is working as it should supply +12.26vdc, did you check the defrost sensors which are in the evaporator and compare their resistance?
I am starting to suspect that ic1 is bad

I did not see a defrost sensor and I dont believe these wine fridges/coolers have them.
Firstly they dont go below freezing.

From the manual:

Using the Temperature Control Panel
The right (beverage) zone of the refrigerator has a temperature range of 34° F to 65° F.
The left (wine) zone of the refrigerator has a temperature range of 40° F to 65° F.

Also, i have owned 2 wine fridges and kept a data logger in them. What they do is turn on the heater at set intervals... say every 12 hours... prevent frost build up. This occurs no matter what temperature the fridge is set to.

I am starting to suspect that ic1 is bad

That would be a shame! But I think you might be right.... We have seen not the slightest sign of life from it. Its like it died with its eyes open...

[R_J]

The power supply is working as it should supply +12.26vdc, did you check the defrost sensors which are in the evaporator and compare their resistance?
I am starting to suspect that ic1 is bad, even if one of the sensors etc. was bad it should produce something on one of the displays, The blown IC3 right off the main microprocessor is not a good sign, Does the microprocessor seem to get warm to the touch?

[KYBOSH]

Lets start from the beginning:
The power supply supplies 12 volts dc for everything. Do you have +12 volts across EC4 ??? when everything is hooked up?
if not then we can check the primary side and see what voltage is ACROSS EC1 and ACROSS EC6

Awesome lesson R_J... i had amnesia regarding the frequencies of transformers. Will review and not forget it again.

One the bench i have a voltage of 12.26V on EC3 and EC4 and the same is true when its hooked up.

EC11 is 5.07v, EC12 is 0v, EC13 is 0V and EC14 is 4.8v but very slowly decreases ~0.02v per second. These behave the same hooked up and on the bench.

[R_J]

This is a switching power supply it operates at around 60KHz if the transformer had even one bad turn the power supply would not work and the switching ic would be blown.
The power supply supplies 12 volts dc for everything. Do you have +12 volts across EC4 ??? when everything is hooked up

What are these "expected readings" you are looking for?

Specifically the PSU is not providing adequate voltage (or any voltage at all) to the accessories and components.

I checked for voltage going to the relays.JK1 has 11.5v going to it

Recall the PSU was only supply 1.2V when it was on the bench....

Lets start from the beginning:
The power supply supplies 12 volts dc for everything. Do you have +12 volts across EC4 ??? when everything is hooked up?
if not then we can check the primary side and see what voltage is ACROSS EC1 and ACROSS EC6

[KYBOSH]

So as I mentioned, I think I have narrowed the problem down to the PSU.
Specifically the PSU is not providing adequate voltage (or any voltage at all) to the accessories and components.

The controller/display is actually getting 12V from the PSU via X4 and X5 connector (VCC + GND) but no backlights show up.
I will have to go back and remeasure voltages on the bench as I realize i made a mistake. I was checking pins against ground but I should have been checking them against (+).
When i realized this I checked the LEDs against their corresponding (+) but i got the same voltage readings. Not sure what to make of that....

I have fresh questions about that EF20 transformer.
Its not giving me any expected readings on the secondary side but I don't have enough experience with them.
Plus I have no idea what voltage its suppose to be putting out as I can discern anything from the part number.

[KYBOSH]

The display panels show nothing. If you press and hold the power button, does it do anything?

My gosh! If only it were that simple. Haha.
I ran down to see about your suggestion when I read it but there was no response from the unit.
I believe most appliances will default to an ON state when plugged into the mains. At least you'll see a status light or some sign of life.

I spent a few hours with this unit today. I wanted to go through everything and be as thorough as possible so I left no stone unturned.
I traced out every wire, checked every sensor/motor/widget and even recorded their resistance for comparison.
I wanted to be absolutely sure the issue wasn't something connected TO the PSU rather than the PSU itself.

This is what I found:
X3 Connector is for the LEFT hand (LH) side of the wine fridge.


On it you have the LH chamber circulation fan (F2), the LH chamber thermostat (T2), LH chamber LEDs (L2, L3) and the LH door magnetic switch (MKG2)
The circulation fan is connected to the board via Red (-) & Red/Black (+) wires. The fan itself is a generic type (brushless, 12V) and has a resistance of 2.295MΩ.
This matches closely to the fan on the RH side (2.163 MΩ)
The thermostat is connected to the board via Pink (-) & Red/Pink (+) wires. It has a resistance of 1.627kΩ. This matches closely to the thermostat on the RH side (1.65 kΩ).
The magnetic door switch is connected to the board via 2 black wires. When the door is open the circuit is open and has no continuity. When the door is closed the circuit is closed and there is a resistance of 0.6Ω. This matches to the switch on the left side (0.6Ω)
The LEDs are connected to the board via a white wire (white LEDs) a blue wire (blue LEDs) and a black wire (+). There are a total of 3 LED modules in each chamber (2 on the side and 1 at the top). Each module was tested and they worked. The Vf (foward voltage) of either the white or blue LEDs (all connected as seen from the PSU side) is ~6.26v. <---- Recall the PSU was only supply 1.2V when it was on the bench....

X9 Connector is for the RIGHT hand (RH) side of the wine fridge. The RH side is the mirror image of the LH side with the expection that it does not hold the leads for the LEDs (this is located on X1 right next to it)



Here you have the RH door magnetic switch (MKG1), the RH thermostat (T1) and the RH circulation fan (F1).
Two black wires for the magnetic switch as before (open when door is open, 0.6Ω when door is closed).
The thermostat is connected to the board via 2 yellow wires. The thermostat has a resistance of 1.65kΩ.
The circulation fan is connected to the board via Yellow (-) & Red (+) wires. The fan has a resistance of 2.163 MΩ.
There is a single black wire (+) which supplies the power to the RH side LEDs.

The X1 connector (Black) is where the grounding wires to the RH LEDs (L5, L6) are located.
The white wire control the white LEDs (V_f = 6.28V) and the blue wire control the blue LEDs (V_f = 6.22V).

The X4 and X5 connectors are for the LH and RH button controls/display, respectively.

The blue lines is (VCC), the black is (-) and the Red & Yellow are Rx and TX lines. I tested each of the climate controllers on the bench by supply 12v to them. The backlight display light up just fine.

The X6 Connector is for the condenser fan

Only a Red and black wire. The fan has a resistance of 2.379 MΩ.

The CN8 Connector is where the AC driven component connects to the PSU.


The heater for the RH chamber is connected via a Yellow (10) and black (7) wires.
The heater has a resistance reading of 294Ω.

The heater for the LH chamber is connected via a Red (9) and black (6) wires.
This heater has a resistance reading of 292.6Ω.

The refrigerator pulse solenoid valve (SDF 0.8 3/2) is connected via a Yellow (2) and black (5) wires.
It has a resistance reading of 0.960 kΩ.

The compressor is connected via a Red (1) and Black wire (4).
The starter relay is measured earlier (5.3Ω) and found to be good.


So I have checked every wire, connector and accessory on this fridge. There are no shorts. Every wire has continuity from beginning to end and no component outside of the PSU seems suspect.
By process of elimination I am confident that the issue is with the PSU.

[R_J]

The display panels show nothing. If you press and hold the power button, does it do anything?

[KYBOSH]

Well without a sensor connected to tell it the temperature, it may think it needs to turn on the heater? I guess at this point you may need to install it back into the fridge to see what it does.

So when I connect the board to the fridge and power it up I get a short beep from the surface mounted speaker and that's it. No sign of life after that. But I will connect everything up and take voltage readings this time.
Will let you know how it goes in the morning.

Thanks for the assist and brainstorming session (mostly your brains!)

[R_J]

Im a complete laymen when it comes to microprocessors Im affraid.
Micro output is internal to the microprocessor?

Also which sensor would you referring to?
Remember the PCB is sitting on my bench and the only thing that is connected to it is the mains power line.
So there would be no input from any sensor it would normally be connected to when hooked up to the fridge.

What would be the next step to rectify or at least verify your ideas here?

Well without a sensor connected to tell it the temperature, it may think it needs to turn on the heater? I guess at this point you may need to install it back into the fridge to see what it does.
here is a similar fridge controller wireing diagram

[KYBOSH]

The microprocessor is outputting 1.75 volts which turns on the ic3 driver pin3.so either the micro output for that pin is bad or the program is turning on that pin to turn on the heater, maybe a bad sensor is causing the problem.

Im a complete laymen when it comes to microprocessors Im affraid.
Micro output is internal to the microprocessor?

Also which sensor would you referring to?
Remember the PCB is sitting on my bench and the only thing that is connected to it is the mains power line.
So there would be no input from any sensor it would normally be connected to when hooked up to the fridge.

What would be the next step to rectify or at least verify your ideas here?

[R_J]

The microprocessor is outputting 1.75 volts which turns on the ic3 driver pin3.so either the micro output for that pin is bad or the program is turning on that pin to turn on the heater, maybe a bad sensor is causing the problem.
This fridge has two zones correct, a left zone and a right zone, It should then have two separate sensors, so I would find a way to switch the sensors on the board and if one of the sensors is causing the problem it should turn off JK1 and turn ON JK2. Or maybe try unplugging both sensors and see what the relays do.

Which plug do the sensors connect to?