voltage regulator problem

[mes64]

I recently ordered 2 of these kits, one for me and one for a student. We put them together at the same time, and now the one he made does not work, while the one I made does. The regulator on his heats up very quickly, and I know there is a short because the Vout and ground pins on the regulator show continuity with my DMM. I checked all the pins as pointed out in another post, and they all show a short, but for the life of me I do not see any bad joints or places the solder might have overlapped onto the ground. The funny thing is that it worked for about 2 minutes when he first connected the power (a 9v plug with 2.1mm center). We unplugged to check mine, it worked, and then put his back in and all the digits lit up dimly and the regulator got very hot within 10 seconds.

I have looked over the board with a magnifying glass, and I don’t see where the problem could be.

Any ideas?

[Michael]

Sounds like one of the pins that is connected to VCC is shorted against the ground plane. It can be any of the pins highlighted in the diagram here:
http://nootropicdesign.com/forum/viewtopic.php?f=34&t=2486

Try removing some solder from each of these pins, and test continuity between the voltage regulator output and ground (two rightmost pins as viewed from top). The short is not necessarily at the voltage regulator — it can be at any of the other pins, too.

There’s probably a bit of excess solder shorting against a tiny bit of exposed copper around a pad. Sometimes copper can be exposed if the solder mask is burned away during soldering. This problem can often be fixed with a little work. Good luck and tell us your results!

[mes64]

Ok I desoldered all the joints ID’d on the picture and checked them out. I don’t see any bridges to the ground anywhere. I am still getting a short. I put a small bit of solder back on the keep things in place. I have included the best picture I could muster up with what I have. Any idea of what I can try now? We have looked at both boards under a magnifier and can’t see a difference between the one that works and the one that doesn’t. Thanks for the help!

[Michael]

mes64,
Please contact orders@nootropicdesign.com to arrange for a replacement kit.

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