LG - Baffling PCB and Linier compressor testing

[GoYamaha]

After all the checks we did below, the LG troubleshooting guide clearly says to replace the PCB but is there anything we are missing that can cause the output from the PCB to the Linear compressor to be absent?  My original failed PCB and a brand new one have the exact same failure symptoms. (PCB part number EBR8380690). To rule out any crazy coincidences that the replacement was bad, we ordered a third PCB.  Now all three have the exact same symptoms.
 

Here's what I know - I am checking for 200VAC on PCB CON201 with the plug that goes to the compressor disconnected from the PCB, more than 30 seconds after Test mode 1 is initiated. No AC voltage at all on the power and common pins. In fact, my meter keeps auto-switching to DC and jumps around between 15 - 20VDC. I have tested my meter on another source to rule out meter issues. 

Other info and previous checks leading to the PCB: 

- Start relay (or overload switch) has continuity. 
- We have normal input power to the PCB. 
- We have 8.5 ohms across two compressor terminals and zeros across the others and all three terminals read open to ground. 
- The 20uf run capacitor is within tolerance at 20.3uf. 
- I rung out the wires from the compressor to the PCB and all is well there.
- Everything in the fridge, fans, buttons, etc operate normally. The compressor simply will not start. 

Thanks! 

[Vance R]

Any blink codes from the compressor inverter led?

[Terry Carmen]

Quote

is there anything we are missing that can cause the output from the PCB to the Linear compressor to be absent?

It will only try to start the compressor for a little while, then give up.

If you check for voltage at the compressor at startup, and see something around 200v or even a little less for a few seconds (don't remember how many, but it's not long), but no running compressor, the compressor is bad.

[GoYamaha]

For Vance - No blinks from the LED except when we disconnect the connector from CON201 in order to check PCB output voltage.  For Terry - As I stated in my write-up, three separate PCBs have no voltage output to the compressor.  What else could cause a brand new PCB with verified input power to have no voltage output to the compressor? 

[Terry Carmen]

16 minutes ago, GoYamaha said:

For Terry - As I stated in my write-up, three separate PCBs have no voltage output to the compressor.  What else could cause a brand new PCB with verified input power to have no voltage output to the compressor? 

A bad compressor can cause no drive voltage.

Unplug CON201 on the board, put your voltmeter on pin 1 and 4 and press the test button once. You should have 200+VAC if the board is good.

 

 

[GoYamaha]

Thank you Terry but as I wrote above in my original post, we did exactly that.  We have no voltage on the power and common pins of CON201 of the original board and two brand new replacement ones. As quoted from my original post above: 

"Here's what I know - I am checking for 200VAC on PCB CON201 with the plug that goes to the compressor disconnected from the PCB, more than 30 seconds after Test mode 1 is initiated. No AC voltage at all on the power and common pins. In fact, my meter keeps auto-switching to DC and jumps around between 15 - 20VDC. I have tested my meter on another source to rule out meter issues." 

 I have been asking the same question on three different forums - What else could cause zero VAC on CON201 of the PCB?  There is no way that three different PCBs can have the exact same failure symptoms.  I appreciate replies of course but people keep telling me to take steps that I already wrote about in my post.

[Terry Carmen]

If you're going back on this again, I'd try a brand new board but check CON201 voltage before connecting the compressor.

It's possible the compressor is killing the board.

 

[Nathaniel Peterson]

@Terry Carmen- We have 8.5 ohms across two compressor terminals and zeros across the others and all three terminals read open to ground.

Doesn't this prove bad compressor?

[Budget Appliance Repair]

1 hour ago, Nathaniel Peterson said:

Doesn't this prove bad compressor?

NO, a LG liner compressor only has one winding so one of the three connectors is always open to everything and the other two are the single motor winding.

[Nathaniel Peterson]

9 minutes ago, Budget Appliance Repair said:

NO, a LG liner compressor only has one winding so one of the three connectors is always open to everything and the other two are the single motor winding.

Didn't know that, never worked on a linear compressor. Thanks!