[JPK]

Check the usual suspects:

• Check you didn't leave the polarity switch on the center position (=mute),
• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Flipped IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

Check the DC voltages:
First check the supply voltages as described in the setup guide.
Next, without any input signal, connect the voltmeter black probe to 0V and check you get no DC voltages on TP2. Any DC voltage higher than a few millivolts shows that the DOA is the issue.

Check the DI input
Check you didn't forget to remove the JMP1 jumper.
Check you didn't swap the 2 transistors on the DI board.
If the DI input works then the issue may be in the switching between DI and XLR. Check the 2N7000 on the DI board. This component is sensitive to static electricity and is better handled without your shoes on (body grounded).

Try to follow the signal
Send a constant 100Hz - 100mVAC sine signal on the input, measured between pins 2&3 of the input XLR.
Check the level with the preamp connected because the input impedance of the preamp may pull the signal down.
Connect the voltmeter black probe to 0V and trace the signal.
On TP1 you should get about 750mVACOn TP2 you should get more than 10VAC, depending on the position of the gain potentiometer.
The reading should follow the input signal level.
The place where the signal drops will give you hints on where to look for.