Voltage reads coming from the monitor pcb.

 

Usually, when a load is connect to a PSU, the voltage goes down, not up.
Since this is a switched mode power supply, SMPS, anything can happen.
We need to go back and look at the voltages coming from the PSU board.

 

Do I look at the voltages before and after connecting the monitor?
Currently, all pcbs are disconnected from PSU.

 

With the voltage rails shooting up to 19.2V instead of 15V, can we say the ADCs are heating up due to that?

 

PSU photos

 

Now that I think about it, here is my synopsis as to what happened.
I said chip capacitors don't usually fail.
The PSU is outputting ±20V. The chip capacitor got 40V across it and failed short circuited.

Remove the PSU.
You will have to trouble shoot the PSU separately with dummy loads.

 

How did the chip cap get 40V? I measured voltage into Audio IO and max was 19v after I connected the monitor PCB.
Without the monitor PCB the voltage into audio io is 15v.

 

I have the PSU out and powered.
I’ll begin checking unloaded.

 

I confirmed the PSU outputs CN1 #1 and #2 go up to 10 +19V and -19.6V respectively after I load them with the monitor PSU.

 

Readouts with then without Monitor PCB.

 

PSU readouts when attaching both Monitor PcB and Audio IO PCB.

goes back closer to spec.

 

PSU voltage output with audio IO connected alone.
also, the audio io logic ADCs don’t heat up when connected without the Monitor PCB.

I stopped testing for tonight.

 

I did one more test. I tested all the monitor PCB components for continuity and found both of these SMD caps reading 0 Ohm, and beep when tested for continuity.

is this normal? Do they need to be replaced?

 

You cannot meter components in-circuit if you don't know what else is connected to said components.
The only correct way is to remove the component from the circuit and then measure while out of circuit.

 

PSU schematics indicate +12V and -12V as nominal voltages. They must have a reason for specifying these values and not +15V and -15V.

There is no voltage regulation on the +12V and -12V supply rails except via the +5V rail.
You need to load the +5V rail with external dummy loads and see how the +12V and -12V rails respond.

Possible suspects are U2 TL431CD, U5 4N35, U4 TOP-246-Y.

 

Happy Friday! Thank you for the tips!!
I'll resume after work

 

You need to load the +5V rail with external dummy loads and see how the +12V and -12V rails respond.

What is a makeshift way to load the +5V rail?
Where in this area should I apply the voltage?

 

I would start off with a moderate load of 10Ω 3W (i.e. 500mA load).
After that you can try two 10Ω 3W resistors in parallel for a 1A load.

I would connect the load at CN1 between pin 3 and 9 (or pin 4 and 10 which ever is convenient).

 

Resistors arrive tomorrow.

 

i attached a 10 ohm 3 watt resistor to CN1 pins 3 and 9. The voltage output was over double.

theDMM also beeped showing a red arrow sign indicating something.