Easy tool to find short on motherboards

[Kripton2035]

Hi everyone,

I would like to share a project I made recently : I adapted a shorty device and added a display.
it becomes a 0.1mΩ meter with surprising stability.
the original shorty project is here : https://hackaday.io/project/3635-shorty-short-circuit-finder
I did one showed here (**broken link removed**) and was pleased with its performances, but it lack a display.

here is a video showing the measuring of some small values resistors :

here another video showing continuous resistance measuring along a soldier roller :

and last another video showing how to find a shorted capacitor on a 820-00165 macbook air motherboard.
fast and easy.

I'm cleaning the schematic and sources, and will share it when it's ready.
just teasing

 

[Kripton2035]

actual state of the pcb.

 

[danadakk]

Here is a ARM core with 20 bit diff input A/D and on chip reference, as well
as Idac, might be worth looking into (get rid of external IA) -

https://www.cypress.com/documentation/application-notes/an84783-accurate-measurement-using-psoc-3-and-psoc-5lp-delta-sigma

https://www.cypress.com/documentation/application-notes/an57821-psocr-3-psoc-4-and-psoc-5lp-mixed-signal-circuit-board

Dev board $ 10 (debug and program)

https://www.cypress.com/documentati...oc-5lp-prototyping-kit-onboard-programmer-and (ignore "out of stock" comment, I thinks they are driving biz to their distributors).

Compiler and IDE (PSOC Creator) free.

Chip has lots of other resources onchip, attached a catalog of them -


Regard

 

[Kripton2035]

thanks for this, but I already know about the cypress psoc. I even have some psoc1 in my drawers...
this was first an arduino project (a teensy in fact) so I extended it using the same components.
the design works with the 10 bits arduino adc, but has a small measuring range (0.4mΩ to 0.4Ω)
so I used another adc ( a mcp3421 in 16b mode) to have a 0.1mΩ to 2.5Ω range.

as the shorty is open sourced, you can make one with this psoc3 or 5 if you want !

 

[Kripton2035]

I've published the first draft of schematic and source code of the project. enjoy !
**broken link removed**

 

[myrivertale]

Your description is somewhat vague and leaves me to make some assumptions.

By "motherboard" I assume you mean a PC system board.
By "multimeter" I assume you mean you are measuring resistance.
By "short all over" I assume you mean measuring across VCC and GND in both directions.

Those are all a lot of assumptions to make but any how, here goes.

Finding a dead short across VCC and GND on a complex system board is one of the most difficult repair jobs to perform.

Generally speaking, it can be a short caused by any one of the many ICs but quite often it is a shorting electrolytic decoupling capacitor. It can also be a short between supply lines. I have seen a short caused by excess solder blob underneath an IC chip that crept under heat and gravity after 25 years of operation.

To locate a short between supply lines you will need a current tracer. I am aware of only one that was ever made by HP, the HP 547A (and I am not going to let you have mine).

Without such a current tracer, you have to use the binary search technique where you cut traces on the board and figure out which path the current is taking.

It might be more expedient to get a new motherboard.