DRO-550 Construction Guide (rev. 2)
4
Step 2. Visual Inspection
The DRO-550 circuit board is professionally manufactured on a modern, surface mount
assembly line. To keep the power buy price as low as possible, the boards are not electrically
tested after they are assembled so there is a possibility that the board has an undetected flaw.
The incidence of these flaws should be very low but it only takes a few minutes to check for the
most likely failure points before applying power and doing permanent damage to the board.
First, we visually inspect the power supply for components installed with an incorrect
orientation. Reference the picture on the left. The red arrows point out the orientation marks for
components that must be placed on the board in a certain way. The orientation marks are small
lines or dots that are marked on the components. There are also small white dots on the printed
circuit board that indicate the correct position of the orientation marks with respect to the board.
For each red arrow in the picture, make sure that the component's orientation mark exactly
matches the position as shown in the picture.
Next, check the ARM7 processor in the middle-left side of the board. It is the largest device and
says "Atmel" in large lettering. Check that the direction of the lettering matches the picture at
left. You can also note that the orientation dot is in the lower, left-hand side on the processor.