how do I check the ground continuity between the boards, as you suggest? I do not see any pin or contact clearly marked as "ground."
On the main board, the pin on the side of the DC barrel jack is a reliable ground. On the display, you can follow the trace from pin 1 to some other location with an exposed pad that you can probe. In general, most boards have a large 'ground plane' covering unused areas of the board that all the ground signals connect to.
Thanks for that. It is rather hard to trace pin 1, for the LCD component obscures most of the board.
Following the instructions found here
for testing continuity, this is what I did:
- I Set my analog multimeter to the Ohms function at x1K scale.
- I Calibrated the meter by ensuring the needle goes to zero (from infinity) when touching both probes.
- With the kit unplugged from the power source, I touched one probe (black) to the pin on the side of the DC barrel jack, and the other (red) to the solder point of pin one on the male connector on the LCD board.
- I also touched the red probe on the exposed part of pin 1 itself.
Both of these tests suggests a closed circuit, for the needle jumped to zero in both cases.
Should this not been an accurate test, kindly suggest which point on the boards I should probe. I apologize for my lack of experience and all the questions, but please understand that I am a novice, and I haven't done any electronics projects in about 20 years.
I just realized that you suggested not to test on or around pin 1. I have tested other points that I believe trace back to pin one on the LCD board, including one of the large soldering points of the LCD component itself (on the edge). These suggest also a closed circuit.