Short between +5v and GND on Controller Board X 2, now what?

Howdy! Thanks to anyone who might read this and double thanks if you can help with this.

After many months of looking at my version shruthi 0.5 digital/control boards, i finally collected parts and started building them a few weeks ago. I’ve finished one of the SRM-4 board and have two controller boards without the lcds soldered on.

Just before I was about to test the srm-4 and the controller boards, I turned on my trusty multimeter and poked around and checked for potential shorts.

And shorts I found. Both controller boards have a short between GND and +5v. I checked the LCD pins 1 & 2 and 15 & 16, and it’s there as well.

I’ve looked all over the controller boards and there’s some less-than-perfect soldering, but I don’t see any solder bridges. The ICs are oriented correctly. I had to clip the resistor network because there was one too many pins, but other than that, all parts are pretty standard and sourced from digikey.

Should I be testing resistance between GND and 5v for clues to where there might be a problem? Is it time to desolder the IC2 and IC3 and replace them? Is it time to desolder everything?? Should I power it up and see what catches fire???!

The fact that it’s both controller boards with the same ground short issue is really troubling.

Any guidance would be helpful.


i just took a quick measure at a v0.7 board, also without LCD soldered, it has about 4.95 kohms between GND and V+
maybe it’s just a hair of copper between 2 pads or something like that

How are you checking for the short?

rosch: it’s simpler than that: to measure the resistance between two points the meter sends a current and measure the voltage (or vice-versa). So the meter is actually powering the whole thing; albeit with an insignificant voltage/current. And the digital board does have lots of resistive elements between GND and +5V. Starting by the contrast trimmer and the 4 pots…

Ok. I may have some egg on my face to clean off… I’ve been checking for the short with the multimeter set to V, which I am now understanding is only for measuring volts. With multimeter leads on +5v and GND, the voltage measures 0.

But after looking at the multimeter manual, there’s a continuity check mode. This measurement shows that there’s an open circuit.

So I’m hoping this is a classic case of panic first [and panic often], read the manual last.

Have we solved a nonexistent problem? If so, thanks. If not, thanks as well.

seems ok. can you measure resistance with it?

> With multimeter leads on +5v and GND, the voltage measures 0.

If the circuit is not powered, this is normal.

…and i Guess it reads 5V if powered…

Yup, powered up the controller boards and I have just a hair under 5v running through the circuit. All the leds are functioning, so all is fine.

Rosch, the resistance between the ground and the 5v on my boards is around 1.6k ohms without the srm-4, and 1.2K ohms with the srm-4 hooked up.

Thanks for all the quick replies everyone. I owe you all a song. But first I have to solder the lcd and tune my ladies. Then I will rock.