Hello there!
I own an Allen & Heath XONE DB4 DJ mixer that suddenly stopped receiving Analog input to all four channels.

With the selection matrix switched to Analog, I tried these steps to confirm the issue was not a simple setting error:

1- I switched out the RC cables – no channel light signal or audio

2- I tried multiple analog audio sources – no channel light signal or audio

3- Hard reset the mixer multiple times – no channel light signal or audio

4- Powered on and off multiple times – no channel light signal or audio

5- Reinstalled the latest firmware - no channel light signal or audio

One thing to note is that the digital input works perfectly fine. I attached a schematic from the user guide that shows the connections coming in. Also attached the service manual, but of course, the PCBs are “proprietary” are blurred out.

With all four channels not reading analog input I have a feeling it’s either the power supply or the DAC component (if common) is where I need to check.

Can anyone here help me similarly to the fellow helped out in the link at the bottom? I need some guidance to locate the bad component and replace it.

I have a multi-meter and can read circuits.
I’ll also share photos in the next day or two showing the PCB.

Link to User Guide:
https://www.allen-heath.com/media/XoneDB4_ug_ap7977_4.pdf

Similar thread:
https://forum.allaboutcircuits.com/...er-need-help-locating-pcb-with-problem.87064/

 

Welcome to AAC!

If you have to tackle this, eventually you will have to open it and have a look.
Try to take and post clear, well focused photos of the internal circuit board.
Look to see if there are any voltage supply markings near connectors.

Your first step (besides a good visual inspection) is to measure any and all supply voltages using a DMM (digital multimeter).

A circuit schematic would be a great help.

 

Hello MrChips
Thank you for getting back to me!
I opened up the mixer this evening and here are some photos.

Photo set #1:
PCB board receiving signal from the Analog input PCB

 

Photo Set #2: PCB connected to the voltage converter output connector

 

Follow up details to photo set#2.

I hope the pictures are clear enough to give me guidance on where to begin voltage checks.

 

Thanks for the photos.
I’ll have a closer look in the morning.

 

Here is the schematic for the power supply.
https://www.allen-heath.com/media/xone_db4_db2_004_066_psu_2.pdf

Now we know the output voltages of the PSU on CN1 and CN2, use a DMM to check the voltages.

 

I'm amazed you found the schematic!!!!!!!!
I have not disassembled the PSU just yet. I will attempt to check it this evening with my current (heavier) probes. I placed an order for precision thin probes will arrive tomorrow in case I'll need them.

Back here soon.

 

You don't have to disassemble the PSU. You just need to access the pins on CN2 at the upper left corner of the board.

You can get at 6 of the 12 pins from the top. The 6 other pins can be accessed from the bottom side of the board.
Be careful and try not to let the DMM probe slip and short out any two pins.

 

Here are the readings.

 

Houston, we have a problem!

https://www.allen-heath.com/media/xone_db4_db2_004_066_psu_2.pdf

 

SICK!!!!!

Do these readings mean CN1 is a bad chip and needs replacement? Or do I need to trouble shoot before it and before we can ID the problem component?

 

We have a very strange situation where the voltage readings are roughly twice the expected values.

My first guess is that something is wrong with your DMM.
Can you check it against a known voltage source such as a standard 9V battery?

 

When I checked the pins on the mixer motherboard, the voltage on the DMM was set to AC 200V range.
I checked a 1.5V battery that way, and registered almost double.

Should I check the board with AC or DV V setting?

 

Checked it again with DMM set to DC.

Updated values below:
Both terminals read the same value
0V
0V
6.9V
3.29V
5.03V
15.47V

 

SICK!!!!!

Do these readings mean CN1 is a bad chip and needs replacement? Or do I need to trouble shoot before it and before we can ID the problem component?

Don't jump the gun. There are a lot of things to be checked first before we issue a verdict.

When I checked the pins on the mixer motherboard, the voltage on the DMM was set to AC 200V range.
I checked a 1.5V battery that way, and registered almost double.

Should I check the board with AC or DV V setting?

So I guessed right!
Set your DMM to 20VDC (or a range 20VDC or greater).
We will get a much better analysis when you post the proper readings.

 

Checked it again with DMM set to DC.

Updated values below:
0V
0V
6.9V
3.29V
5.03V
15.47V

Ok, there is one more measurement we are looking for which could be on the other set of pins.
We are looking are a negative DC voltage reading.

 

Yep, I had a feeling I jumped the gun there.

To make sure I am doing this right.
The black terminal of the DMM is connected to the ground of the mixer (basically the board with a ground sign on it).
Then checking the pins recording voltage.


By another set of pins, which ones are you referring to?
The ones I checked are all 12 pins. The 6 L-shaped ones and the ones from the back side of the board. All +ve voltages.

 

Ok. We have a problem showing with the +12V and -12V supplies.
I have to go out. We will carry on later.

Disconnect the power plug. Don't do anymore live testing.
We will have to open up the PSU and test some diodes.
See if you can post some photos of the PSU board.

 

Understood.
I’ll provide a clear photo.

I carefully re-tested each terminal and attached a labeled photo. Catch you later, thanks!