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Printed Circuit Board Assembly & PCB Design Forum

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Pcb component testing

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#86010

Pcb component testing | 17 December, 2020

Hi all Wonder if anyone can help , I'm trying to test a pcb board ( with very little experience) I've tested the resistors and now the capacitors , only to find that about 5 of them have continuity so guessing there not working . I checked the same on a board that I know works only to find that the same 4 capacitors have continuity but the board functions fine Am I missing something with my lack of experience Regards Chris

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#86011

Pcb component testing | 17 December, 2020

Unless you have a firm grasp on the circuit and electronics in general, you are on a hiding to nothing. Testing components in circuit is complex, because its a circuit and any measurement you make is affected by connected neighboring ones. If you set a multimeter to continuity and put it across capacitor it will show continuity until the capacitor charges up and then it stops. A capacitor is essentially two metal plates with a gap between them - there is no continuity, but it does store charge which is what you are seeing. This is why they are used, they can smooth out blips, or make up parts of filter circuits.

As a very crude rule, if something has failed its quite likely to be in the power regulation stage like a large electrolytic, a blown fuse, a burnt out resistor. Or an IC you can do nothing about because its full of custom code...

With knowledge and a diagram (or measurements from a running powered up board) you can narrow down what part of a circuit doesn't work by checking things starting with the basics like "is it getting power" but without that information you are stuck with spotting the really obvious common stuff like fuses or that part is black and clearly burnt/gone pop.

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#86463

Pcb component testing | 30 March, 2021

This is correct. We don't know if you are looking across the components or referencing a point they are not even connected to.

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