- The LaST Upgrade -
Part 43 - FINDING A SHORT
Last updated March 6, 2023
Here is a quick lesson in fault finding a power rail
short with a low resistance meter.
First up, a proper low resistance meter.. |
||
Basically what we do is check the resistance across various
capacitors around the board and look at the resistances.
I started at the bottom right corner of the board working my way up with and to the left taking note of the resistance. Which is 84.2mR.
|
||
Moving upwards on the board you can notice the resistance gets slower, so we are getting closer to the short! Now 35.9mR!
|
||
Now I can only move to the left. So moving along one by one the resistance got lower and lower until there was nowhere else to go...
|
||
This is the lowest resistance point on the whole board on
the power rail at 11.3mR.
So checking what capacitor that is on the PCB files...
|
||
..And yes this was a PCB oopies the problem!
I have also diagnosed failed ceramic capacitors on motherboards this way as well.
|
||
Overall a low resistance meter is a very useful piece of kit when you have something short circuit on the motherboard. Like on the power rails and have no idea where short actually is.
|