I’m going to be fully away for the rest of today due a volunteering event.
Please send me any other checks needed on the board and I’ll get them back tonight

 

Ok, thanks.
I am not able to replicate your measurements. All of my measurements are higher than 1MΩ.
I have to think about this.

 

Am I necessarily measuring incorrectly?

attached some close ups.

 

I cannot see a way out of this and it looks like you will have to remove the Cirrus Logic CS5368 IC.
Do you think you are up to the task?

Don't do anything rash. I need to look for another way to test this.

 

I’ll be honest I am not.
But if I research it enough later tonight, I will be by tomorrow. I need to make sure I have the correct size solder tip. I did receive the flux today which helps with making sure the solder sits where it needs to be.
Is there a way I can check the CS5368 for proper functionality without removing it?
Is there a schematic you can send me for it?

 

I’ll be honest I am not.
But if I research it enough later tonight, I will be by tomorrow. I need to make sure I have the correct size solder tip. I did receive the flux today which helps with making sure the solder sits where it needs to be.
Is there a way I can check the CS5368 for proper functionality without removing it?
Is there a schematic you can send me for it?

Is there a way I can check the CS5368 for proper functionality without removing it?

Maybe, but it is not that simple.

Here is the scenario.

Analog signals go to a set of opamps, either 072 opamp or 5532 opamp.
It appears that the output of the opamp goes to a 100Ω series resistor and to the analog input of the Cirrus Logic CS5368. This is the ADC.

https://statics.cirrus.com/pubs/proDatasheet/CS5368_F5.pdf

As I mentioned before, something is drawing a lot of current from the +12V supply and feeding it to the -12V supply. This causes one of the resistors to go bad. The opamp outputs are now rising up beyond +9V which would likely destroy the CS5368.

We need to have the -12V supply fixed first.
I think removing the CS5368 will allow us to correct the -12V supply problem.
Then we would install a new CS5368.

 

Ok.
I will return on this in the evening.

 

Here is something to try.

Remove the two 100Ω resistors (SMD code 1000).
This will isolate the 5532 opamp from the CS5368.
Repeat the resistance measurement from pin-1 to pin-4, and from pin-7 to pin-4 of the 5532 opamp.

Also measure the resistance to GND from the resistor pad that leads to the Cirrus Logic CS5368.

 

I will follow up this evening. I had to skip last night.

 

I will get back here on the check, but wanted to add this data sheet for the Logic. Could by any chance a short from the Logic chip cause what’s going on?
If so, which terminals should I check for short?

 

It is possible that the CS5368 inputs are damaged.
This is an 8-channel differential input ADC. Hence there are 16 input pins.

The test that I proposed in post #88 should be able to give us some clues.

 

Remove the two 100Ω resistors (SMD code 1000).
This will isolate the 5532 opamp from the CS5368.
Repeat the resistance measurement from pin-1 to pin-4, and from pin-7 to pin-4 of the 5532 opamp.

Pin-1 to Pin-4 (black probe on pin 1
550 ohm Same readout as the other ICs
Pin-1 to Pin-4 (red probe on pin 1)
1605 ohm Same readout as the other ICs

Pin-1 to Pin-7 (black probe on pin 1
1.7 ohm @200M dmm range not same readout as the other ICs
Pin-1 to Pin-7 (red probe on pin 1)
1.3 ohm @200M dmm range not same readout as the other ICs

 

I need to see the resistance reading, RED lead at A, BLACK lead on GND.
Also RED lead at B, BLACK lead on GND.

 

RED lead at A, BLACK lead on GND

where on the board shall I ground?

 

I grounded back to pin 10 on Logic chip.

A read 1.0 at 200M range
B reads 1.0 at 200M range

 

Use the ohmmeter and check if there is close to zero ohms between any two of these points.

 

All of them are close to zero.
A beep sound if switched to that option.

 

All of them are close to zero

Ok. Use the mounting hole as your ground.
Set the meter to 20K or 200K.

 

Ground as mounting hole, measuring back to the 4 spots at the capacitors, all four readings are zero ohm

 

Ground as mounting hole, measuring back to the 4 spots at the capacitors, all four readings are zero ohm

Ok, now we are looking for readings from point-A to GND.
Then from point-B to GND.