Finding a power rail short with a low ohmic meter

[exxos]

Here is a quick lesson in fault finding a power rail short A low resistance meter.

First up, a proper low resistance meter..

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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.

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Moving upwards on the board you can notice the resistance gets slower, so we are getting closer to the short! Now 35.9mR!

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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...

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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...

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..And yes this was a PCB oopies the problem.

I have diagnosed failed ceramic capacitors on motherboards this way as well.

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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.

[UnderTheRain]

There's a good video on YouTube an TV repair engineer shows you how to fix a TV doing this and then he showed you how to build your own meter.



He gets the circuit from an old electronics mag it works really well

Brian

[UnderTheRain]

Oh I forgot another way way is to use a flir usually your short gets very hot very fast I use the flir on my phone for exactly this. I got this phone specifically for the flir.

Utr