Notice that the D7 pin is adjacent to a ground pin, and
the W-CLK is on the other side of the D7.
Perhaps the plug/unplug cycles have messed up something in
the area of the pins.Maybe stirred up a solder splash that
creates a short. Do a resistance check to ground, inspect
under high magnification, and reflow the solder joints in
Did some more testing on the Arduino and main board,
trying to replicate the pulses shown in your photos on
I found that, with the AD9851 pulled from the main
board, the pulses acted pretty much the same as your
photos and had levels of about 5 v. From that, I
conclude that the Arduino is probably working as it
I then replaced the AD9851 and powered it up. At
that point, I found that the D7 and W-CLK lines had
multiple pulses as before but the levels on these
lines were only around 0.2 v. My guess is that
something is holding these two lines to a low level.
Next step seems to be to try a new AD9851, unless you
can think of another explanation.
Thanks for the help.