Ambika - continuity issues

Hello all, I have completed my ambika mobo (from a kit), but have not yet plugged it in or put in any ICs (other than the three soldered directly on the board). I got to the point in the instructions regarding power supply testing. I am getting continuity between the GND and all four coloured points (although perhaps not between GND and red). I also have continuity between the blue dot and the other colours as well. There also continuity between green and yellow. There is no continuity between yellow and red.

I have been over the board carefully and can’t see any issues with the solder (other than perhaps on the small three surface mounts on the SD card reader - which I understand from the instructions shouldn’t matter.

I can certainly post pics (tomorrow) - just wanted to make sure there is nothing even more obvious to check first…

Not a great first post here, but I need some help. I got an Anushri built without any issue.

Thanks in advance.

Hi deleuzer,
How are you measuring this? Can you post a hi res pictures of both sides of you board?

Thanks shiftr, before I upload pics, can you tell me what readings I might expect? I am using a multimeter to test for the shorts. My meter buzzes if there is less than 60 ohms resistance between two points (so based on the below its not buzzing, but I get resistance readings). The measurements I am getting are as follows (in ohms, as the below are just resistance measurements):

gnd to +5v = 1400

gnd to +3.3v = 1655

gnd to +8v = 1800 (approx.) dropping to 1 (which is the default for open connection, not 1 ohm) after 1 to 2 seconds

gnd to -8v = 213

+5v to +3.3v = 581

+5v to -8v = 458

+5v to +8v = 1400 (approx.) dropping to 1 (open connection) after 1 to 2 seconds

+3.3v to -8v = 900

+3.3v to +8v = 1400 (approx.) dropping to 1 (open connection) after 1 to 2 seconds

-8v to +8v = 1 (open connection)

So perhaps this is much ado about nothing? Perhaps these resistances are within normal limits?

I also just noticed that if I reverse the position of the prongs (+ve & ve) for these tests, I get different results eg the problematic "gnd to 8v = 213" becomes “1800 (approx.) dropping to 1 (open connection) after 1 to 2 seconds”. All of the above measurements change if reverse the prongs I didn’t expect that.

Thank you!

This is normal. The meter probes are sending current through the circuit and it is “reacting” to it, creating a voltage. What you are trying to detect are shorts (which translate by a resistance lower than 1 ohm), and there are none of them here. I think you expected higher values - but then it would mean the circuit would not do anything interesting at all :slight_smile: