Wine and Beverage Cooler Control Board Repair Attempt

[KYBOSH]

Trying to a fancy Wine and Can Beverage Cooler which wasnt working.
Model number AWBC242GGFD
Previous owner states that it needs a new motor.


When plugged up you hear a quick chime from the PCB alarm but it quickly dies away (trails off actually) and there is no sign of life from the unit at all.
I pulled out the main control board to give a look.




Fuses checked out okay. All diodes except one checked out. It was reading in both directions so I pulled it out of circuit and checked it again but this time it read good.

After some inspection I noticed an IC which looked a bit off even from under the conformal protective coating.

Sure enough I think i found a pinhole in the IC.




Question is... what's the best way to ID this IC?
I could try to get as much of the coating off the chip as I can in order to read what is left of the markings but with the hole dead in the center I doubt I'd be able read it properly.

Any advice would be greatly appreciated!

Thank you in advance!

[KYBOSH]

Got some paint stripper and acetone and got it cleaned up.
I dodged a bullet as the hole JUST missed the manufacter's part number.
This appears to be a Three-way 50V SOP-8 Darlington Transistor Arrays from LANKE.
I have no experience with these transistors so I will do some research as I look for a suitable replacement.

If anyone knows of a good local (US mainland) source for these I'd appreciate the tip.
Im only seeing them on Aliexpress.

Edit to add:
Just placed an order with AE.
Time it would take to find someone local (if they even exist) I will have already received the package.
10 ICs for $4US is hard to beat.

[stj]

ULN2001D - thats a driver - so you need to see if what it drives is shorted.
the datasheet is incomplete and only seems to show the pinout for the 7way version

[KYBOSH]

Thank you STJ.

I found the SOP-8 datasheet but it is on Chinese and impossible for me to discern much from it without a translation. Dont know how to translate a pdf file though.

[stj]

it's the same as the datasheet i posted just shorter,
B's are inputs, C's are outputs.
E is ground and COM goes to the positive supply to the thing it drives.
unless it drives inductive loads like relays or solenoids you wont even need COM, it's just for the reverse protection diodes.

[KYBOSH]

it's the same as the datasheet i posted just shorter,
B's are inputs, C's are outputs.
E is ground and COM goes to the positive supply to the thing it drives.
unless it drives inductive loads like relays or solenoids you wont even need COM, it's just for the reverse protection diodes.

So should i follow the 3rd track to see where it leads in order to find any potential shorted components?

[KYBOSH]

Im having a look at the pics of the driver and I dont see anything inline (direcly connected to it) which would be shorted.
The traces leads to a relay (3C/output) and to the controller chip (3B/input).
The input also terminates to a blank whole where a through-hole resistor would have been.


I will clean off the controller chip to check if it is damaged as well. If i can find a datasheet I maybe be able to determine where that pin is connected to and see if there are any shorted components upstream.

[redwire]

The IC has three output drivers which are driving the relays. BUT one output also goes to the red connector X6 so whatever connects there is shorted.
The IC is like a half or mini version of a ULN2001.

[KYBOSH]

The IC has three output drivers which are driving the relays. BUT one output also goes to the red connector X6 so whatever connects there is shorted.
The IC is like a half or mini version of a ULN2001.

Good eye redwire.
I didnt see that.
I went to check and its the connector for the fan that blows over then condenser.
It reads 2.4Mohms which is in-line with similar computer case fans i have laying around.
l cleaned off the controller chip and it looks perfectly fine.



I tested the 3 relays by running 12V across the leads and they all work fine with healthy clicks.

[redwire]

Um I wouldn't trust a 2.4MEG reading to tell me the fan is OK. Power it up see how it does on 12V. What is X6 3rd pin for? I wonder if the LED strips are OK, not shorted or if they are what goes to the blown IC.
Don't apply 12V power to a relay coil in-circuit, that causes reverse current to flow. I would check the IC did not short 12V power to the input pins, that would take out the MCU as well.

[KYBOSH]

Um I wouldn't trust a 2.4MEG reading to tell me the fan is OK. Power it up see how it does on 12V. What is X6 3rd pin for? I wonder if the LED strips are OK, not shorted or if they are what goes to the blown IC.
Don't apply 12V power to a relay coil in-circuit, that causes reverse current to flow. I would check the IC did not short 12V power to the input pins, that would take out the MCU as well.

Right on Sir.
Fan checks out. pulls 0.063 A on 12v.
The 3rd (middle) pin on X6 is connected to absolutely nothing.
Seems to be simply serve as a guide or support.

Interior lights LED use 3 wires (white, black, blue) and come from the X3 connector.
The LEDs tested good at the connectors.

Not sure what else i can check without a replacement darlington.
I am getting 12v to this transistor as it does get hot when plugged in (confirmed via FLIR).
From a quick glance the darlington activates the 3 relays there which power up the compressor or something hefty as they are connected to the connector with the thick gauge wires.


Edit to add:
thanks also for the tip on not running testing relays while in-circuit. Im not familiar with the perils of reverse current but I will look that up as well.

[stj]

i would test the relays with a 9v battery to make sure they click,
other than that, these chips can randomly fail.
i have maybe 50 or more of the 8way version, i use them to fix gambling machines that use them for all types of stuff.

[redwire]

This thread I posted what happens when you power a relay on a board that has power off- current flows backwards. Using a bench PSU or maybe the 9V battery. It's best to have the board under it's own (12V) power and just ground the relay pin, shorting the driver output to GND to click the relay - although this doesn't tell you much anyhow. I've heard a click but burnt contacts left it open-circuit some of the time. If it's welded closed, the load would stay on.

Did the insulation in the relay fail, contacts to coil?
Fridge compressor motors generate huge spikes when the relay/contactor opens. I had a big ice cream machine 208V that would start an arc across the terminal block due to this (I added a MOV), and another cooler that would eat contactors up they only lasted a year. I think it also bags the motor if the winding's insulation gets damaged. This is the 4-6kV league.
If this compressor generates a HV spike, it might have made it the over to the relay coil and thus destroyed the driver IC. Or maybe a mains spike did it.

[KYBOSH]

So i got the Darlingtons in today and i promptly installed it on the board.
Sadly the unit did not spring back to life.
I pulled the board and started looking around for anything that i missed, diodes, resistors, transistors. They looked okay.
Started pulling the ceramic caps off the boards to test them.
Came across C2 and it was cracked at the top end cap.
You would have never have known unless you actually went to desolder it off the board.
C8's value fluctuates as well. Between 400-600 nF.

My question is what value do you guys think that cracked and dodgy ceramic caps are??
Im also not sure about C9. Its reading in µF where as everything else is showing reading nF.

Thanks in advance!

[KYBOSH]

This thread I posted what happens when you power a relay on a board that has power off- current flows backwards. Using a bench PSU or maybe the 9V battery. It's best to have the board under it's own (12V) power and just ground the relay pin, shorting the driver output to GND to click the relay - although this doesn't tell you much anyhow. I've heard a click but burnt contacts left it open-circuit some of the time. If it's welded closed, the load would stay on.

Did the insulation in the relay fail, contacts to coil?
Fridge compressor motors generate huge spikes when the relay/contactor opens. I had a big ice cream machine 208V that would start an arc across the terminal block due to this (I added a MOV), and another cooler that would eat contactors up they only lasted a year. I think it also bags the motor if the winding's insulation gets damaged. This is the 4-6kV league.
If this compressor generates a HV spike, it might have made it the over to the relay coil and thus destroyed the driver IC. Or maybe a mains spike did it.

redwire
stj
Any advice on the ceramic cap situation above?
Thanks in advance

[redwire]

C8's value is written under it, observe the same text above C9. "105" so a 1uF decoupling cap I think.
Check if you have DC power 12V (for relays) and 5V for the MCU from Vreg? U1.

[KYBOSH]

C8's value is written under it, observe the same text above C9. "105" so a 1uF decoupling cap I think.
Check if you have DC power 12V (for relays) and 5V for the MCU from Vreg? U1.

What a delightful tip! I did not realize that those numbers were the values for the SMDs!
I cant remember ever seeing values printed on the board like that.

[redwire]

Some of the boards out of china have part values written on them, here and there. Usually resistors but the oddball (bigger) caps standout as well.

[KYBOSH]

Some of the boards out of china have part values written on them, here and there. Usually resistors but the oddball (bigger) caps standout as well.

Thanks for the tip! I studied up on decoupling capacitors last night.
You are correct by the way: 105 is code for 1uF. I think i change out C8 and C10 for fresh ones.
The other ones seem to be rated for 100 nF so I will swap out C2 and C15 for fresh ones as well.

I'll check for voltage after I get those sorted.

[KYBOSH]

C8's value is written under it, observe the same text above C9. "105" so a 1uF decoupling cap I think.
Check if you have DC power 12V (for relays) and 5V for the MCU from Vreg? U1.

So it took me a while to get my book of assorted diodes and caps in but i finally got it and replaced the questionable caps.
Still no joy though. Cant figure out what's wrong with this board. I tested the resistors again. Some where reading low on the board but good when taken out of circuit.

I checked for voltage going to the relays.
JK1 has 11.5v going to it, while the others (JK2 and JK3) have none.
Two things funny about JK1 (JZC-32F). When I looked at it with the FLIR it was markedly warmer than the rest of the board.
I thought it might be shorted but then I took it out of circuit and tested it test fine (although in retrospect i tested it at 30V rather than the nominal 12v... will go back and check it again).
Next I checked U1 for voltage.
At first the readings were dodgy but after touching up the solder joints i was getting a solid 11.52 and 5.02 between pins.

Not sure where to go from here....

Of note, when I was testing the electrolytic capacitors next to the small transformer i mistakenly put one in backwards.
When i installed the board back unto the fridge the control panel inside started lighting up but it was blinking off and on.
This went on for a few seconds until i unplugged the unit to have a look at the board again and I immediately noticed the mistake I made.
So this sign of life is good news. I just have to figure out what I am missing. Doesnt seem to be a short but I cant find the bad component.
It could be a fault IC/Controller but I dont know how to test for that.

edit to add:
just checked that relay and applied 11v to it and it works just fine.