Yes it does have compressor. It is 10 years old....

I know you're looking at other things, but does the compressor have a start capacitor? In my experience that's the primary cause of failure in refrigerant-based coolers. I keep a spare for my A/C on hand.

 

I know you're looking at other things, but does the compressor have a start capacitor? In my experience that's the primary cause of failure in refrigerant-based coolers. I keep a spare for my A/C on hand.

Yes I tested all of the components tied directly to the compressor...overload...etc....they all tested out good....

And the relay drive circuit is definitely the issue as confirmed by low voltage readings at both the relay coil (ground side) itself and the base transistor is reading only .5v

Thank you for your input though...I'm taking the transistor off the board and going to test it...something I should have just done a while ago....not 100% this is the problem but I'm really leaning towards it from all the evidence I have gathered.

 

Suspect both scenarios.
You could replace the transistor and diode and/or try tracing the source of the base voltage.

I think my issue is low base voltage from control....I am getting 2.09 volts coming into the board...it then travels to the resistor (1k resistor and I piggybacked another 1k resistor to lower the ohms to 500)

I'm still getting .5v to the base best case scenario....I think my problem is low voltage coming into the board...I have absolutley no idea what to do now to troubleshoot the other board that is controlling this relay circuit. 2.09 volts is way too low....I think I should be getting 3.3v....if I got the 3.3v my problems would be resolved

 

So the transistor checked OK?

 

So the transistor checked OK?

Yes it did....I even replaced it anyway...

Voltage to the board is low....I got it at 2.61 before...now today it is 2.09...I even piggybacked another 1k resistor to drop my resistance from 1k down to 500ohms in attempt to get more voltage to the base

 

So the transistor checked OK?

Something on that display board is not allowing the full voltage to come through...I don't know how to troubleshoot....not sure how the voltage is distributed...bad microcontroller? Bad ground...don't know what to test for and what is normal reading vs what isnt...I'm strongly assuming I should be seeing 3.3v

 

If you assume that the transistor is ok (it has been replaced) then if the Vbe that you are measuring is 0.5 volts then it would suggest that the current flowing into the base of the transistor is very low.
Is there a bad connection between the source of the drive signal ( the display board ) and where it connects to the base resistor?
Can you measure continuity between these points?
Also, unless you are using an oscilloscope to measure the drive signal( the 2.09V) you can’t be sure that the signal is at a steady level. If it is fluctuating rapidly then a dvm will give an average reading.

 

If you assume that the transistor is ok (it has been replaced) then if the Vbe that you are measuring is 0.5 volts then it would suggest that the current flowing into the base of the transistor is very low.
Is there a bad connection between the source of the drive signal ( the display board ) and where it connects to the base resistor?
Can you measure continuity between these points?
Also, unless you are using an oscilloscope to measure the drive signal( the 2.09V) you can’t be sure that the signal is at a steady level. If it is fluctuating rapidly then a dvm will give an average reading.

I will try to measure continuity on that wire that goes from the display board to the board that I am having issues with....

I agree that a cheap DVM only gives me average and it could be bouncing all over the place....but the fact that I am getting 2.09v is problematic regardless of if it is a steady low reading or if it is bouncing all over...

I understand very basic stuff about relays but how this voltage is "created" is above my league and I have no knowledge on this....this is why I don't know how to test for why this voltage is low....I wouldn't know the first thing to check besides simple continuity test on the wire that connects both boards....

 

If you assume that the transistor is ok (it has been replaced) then if the Vbe that you are measuring is 0.5 volts then it would suggest that the current flowing into the base of the transistor is very low.
Is there a bad connection between the source of the drive signal ( the display board ) and where it connects to the base resistor?
Can you measure continuity between these points?
Also, unless you are using an oscilloscope to measure the drive signal( the 2.09V) you can’t be sure that the signal is at a steady level. If it is fluctuating rapidly then a dvm will give an average reading.

Got .007 continuity on that wire....there is something going on with the display board not sending down enough voltage. I haven't a clue where to look...

 

To Macknumber9

2.09 V reading on the DVM is not OK, in any case.
If DVM indicates 2.09V , it can be pure DC voltage or a bouncing. Add a 1 uF capacitor in series to DVM probe and check in ACV mode same circuit. Your DVM should read near 0 volt, if it is pure DC voltage

 

Nice clear image of the display board. I can see the silk screen legend COMP adjacent to the 11 way connector which I assume is your troublesome signal.
Using your DMM on resistance or preferably beep mode are you able to trace that COMP signal back from the connector into the board? Obviously if the display board is multi- layer (4+ layers) this may prove too difficult in which case you’ll need a replacement board to progress.
I had a look at a youtube video of a guy replacing a very similar board in a Vinotemp cooler and the board looked fairly uncluttered on the top side so you may be able to trace COMP back to it’s source.
If this turns out to be one of the pins on U1, which is probably a processor judging by the silk screen JTAG labels close to this device, the board is a dustbin job unless you find an issue with the track on the way.
Just for piece of mind, measure the 12V that can be seen next to COMP.
I can see a silk screen GND label below the connector so there should be a gnd nearby for your probe.

 

Nice clear image of the display board. I can see the silk screen legend COMP adjacent to the 11 way connector which I assume is your troublesome signal.
Using your DMM on resistance or preferably beep mode are you able to trace that COMP signal back from the connector into the board? Obviously if the display board is multi- layer (4+ layers) this may prove too difficult in which case you’ll need a replacement board to progress.
I had a look at a youtube video of a guy replacing a very similar board in a Vinotemp cooler and the board looked fairly uncluttered on the top side so you may be able to trace COMP back to it’s source.
If this turns out to be one of the pins on U1, which is probably a processor judging by the silk screen JTAG labels close to this device, the board is a dustbin job unless you find an issue with the track on the way.
Just for piece of mind, measure the 12V that can be seen next to COMP.
I can see a silk screen GND label below the connector so there should be a gnd nearby for your probe.

What do you mean it's a dustbin job? Just a poorly made board?

I tried tracing and it is so hard....I got continuity from the 4th pin up (which is the comp pin) to a diode....but from there I lost it all....I can't get anymore continuity...I'm tempted to run this thing so it spits out the 2.09 volts and just check for that 2.09 everywhere on both sides of the board....

I know it's probably hard to say but could a bad microcontroller cause loss of voltage? Or would this be more likely an issue with a failing component such as a diode or capacitor etc?

I already doubled up my resistor....I piggybacked a 1k resistor on top of 1k resistor to get 500ohms of resistance...I'm tempted to add another one which I believe would give me 333 ohms...maybe I need to add them all up so I can finally get the .7v that I need....but what was weird is I read 2.69v before and now I'm reading 2.09v

 

I'm assuming this 12 volts that comes in has to go somewhere and be stepped down to the voltage needed for run this compressor relay...which I'm sure is most likely 3.3v...any idea which component that might be or is this something internal to the microcontroller that handles this step down? I would have to assume this is where my problem lies...in the step down process...although I guess it could be something else still...bad diode perhaps

 

Nice clear image of the display board. I can see the silk screen legend COMP adjacent to the 11 way connector which I assume is your troublesome signal.
Using your DMM on resistance or preferably beep mode are you able to trace that COMP signal back from the connector into the board? Obviously if the display board is multi- layer (4+ layers) this may prove too difficult in which case you’ll need a replacement board to progress.
I had a look at a youtube video of a guy replacing a very similar board in a Vinotemp cooler and the board looked fairly uncluttered on the top side so you may be able to trace COMP back to it’s source.
If this turns out to be one of the pins on U1, which is probably a processor judging by the silk screen JTAG labels close to this device, the board is a dustbin job unless you find an issue with the track on the way.
Just for piece of mind, measure the 12V that can be seen next to COMP.
I can see a silk screen GND label below the connector so there should be a gnd nearby for your probe.

In this picture I get continuity from the compressor pin to the left side of that diode labeled "d1"...I look at the traces and I don't even see it leaving the diode and going anywhere except up to those resistors

 

In this picture I get continuity from the compressor pin to the left side of that diode labeled "d1"...I look at the traces and I don't even see it leaving the diode and going anywhere except up to those resistors

Ok I got pin 5 continuity...pin #5 on the u1 chip...I'm assuming the u1 is the microcontroller...I get excellent continuity..... .001

 

I think I can see the track which connects to D1.
On the other side of D1 that has the + silk screen label a track appears to connect to a via ( round pad with a hole) between the bottom of R22 & R21 that will route this track on the other side of the board.
Is this the side of the diode that connects to U1 pin 5?
What voltage do you measure on U1 pin 5 when you are measuring 2.09V on COMP?
Dustbin job was meant to imply that any issue with the processor would not be fixable.

 

I think I can see the track which connects to D1.
On the other side of D1 that has the + silk screen label a track appears to connect to a via ( round pad with a hole) between the bottom of R22 & R21 that will route this track on the other side of the board.
Is this the side of the diode that connects to U1 pin 5?
What voltage do you measure on U1 pin 5 when you are measuring 2.09V on COMP?
Dustbin job was meant to imply that any issue with the processor would not be fixable.

I am going to attempt to get the reading at u1 pin 5 now...if it reads the same shitty low 2.09 volts then I know it has to be the microcontroller and then there's nothing I can do right?

 

Unfortunately that is probably true, but let’s see what the voltage is.

 

I think I can see the track which connects to D1.
On the other side of D1 that has the + silk screen label a track appears to connect to a via ( round pad with a hole) between the bottom of R22 & R21 that will route this track on the other side of the board.
Is this the side of the diode that connects to U1 pin 5?
What voltage do you measure on U1 pin 5 when you are measuring 2.09V on COMP?
Dustbin job was meant to imply that any issue with the processor would not be fixable.

Ok I got the reading...it was very difficult but I got it....same crappy low voltage....2.45.....which is the exact same number everywhere else....

Bottom line is the voltage is just as low at pin 5 of u1 as it is on the entire board on that trace and on the board with the compressor relay on it...

I guess I can safely junk this now because I can't just throw any microcontroller in....it needs to be programmed to work with this machine. Correct?

 

Unfortunately replacing the micro is not an option even if you knew the generic part number.
Before you junk the board just probe the pins of U1 and satisfy yourself that the device is getting what appears to be a sensible voltage on one or more of it’s pins, excluding pin 5, that could be VCC.
It could be 3v3 or 5V, I believe you thought the board ran from a 3v3 supply, check for this on U1.
If that looks ok then the processor port on pin 5 is probably defective and it’s either purchase a replacement board or junk the cooler.
To give you an idea of replacement cost ebay has a very similar board labelled Howden wine cooler display control board 082641452 for about $42.