[Greg]

I just finished putting together the AB528 and mic input works fine and seems to be doing what it supposed to. The only problem I have run into is that the DI doesn't seem to work. I can turn it up  full and hear white noise but, no other signal than that. I also don't hear the relay switch click when I insert cable. All of the connector connections on the DI board check out. Any suggestions or troubleshooting I could do? 
Thanks in advance!

[JPK]

Does the XLR input still pass through when there is a plug in the DI input?

[Greg]

Hi there, thanks for getting back to me, much appreciated and apologies for late reply!

I just had another look and I do actually hear the sound of the relay clicking. Still not getting any signal from the DI. 
Have tried using a mic and then plugging into DI the mic signal does shut off. 

[JPK]

Send a 1VAC sine signal into the DI input and check if you can measure it on U2 pin1 (the square pin) against 0V. You should read 1VAC on the meter.
Also check there is no DC voltage on this pin.
If all OK, the issue must be on relay RLY1.

[Greg]

So it has been roughly a year since I've had the time to come back and work on this again but I did the 1vac sine and everything passed and no dc. If it is a problem with RLY1 where should I test next? Should I replace RLY 1and RlY2?

[JPK]

If the DI signal is present on U2 pin1 then the issue can be in the J4a/J4b connector, check the solder joints.
If OK, try changing RLY1.