pcb home work help

Community PCB Design
1

I have some home work to study and wondering if anyone can helps , My objective is to name all these components from a laptop motherboard and test them with a multimeter ,

I will go thought what I have done to test and if I am wrong in anything then please tell me.

From my picture number 1 . power choke coil or inductor / continuity test - Beeps / Resistance 0.3 . I think the test says its good and it should beep , not sure about resistance value I think zero is bad

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  1. Diode / Continuity - No beeps / Diode on multimeter .0L . I think this is bad because of the .0L reading

3… Capacitor , No Beeps / resistance mode . 4.000 Ohm starts of and move up in value , I think this capacitor is ok but I am not sure . mesr meter reads 0.010 which is low and the capacitors don’t have the values on them to work out, so I am some what confused and the readings on these small caps.

  1. Capacitor No beeps / . resistance 0.700 ohm and moves up , mesr 0.010 . not sure these readings are good or bad they seem quit low .

Any help with this will be very appreciated .

SXY69rq.jpg5120×3840 1.03 MB
https://i.imgur.com/SXY69rq.jpg?1

2

Hi Katie,

Let’s go through what you’ve found so far.

  1. Inductors will generally be low resistance. I did a quick Digikey search for “2R2” inductors and 0.3 Ohms is in the realm of possibility for them. Depending on what you are using for a multimeter, you may not be able to accurately measure resistances that low. If you can’t find the part’s datasheet to see its specific properties, you may have to do more advanced testing to determine if the inductor is healthy.

  2. Think about the properties of a diode and what it does to DC voltages. With your meter in “Diode” mode, what happens if you measure the diode backwards (flip your probes to the opposite terminals)?

  3. My best guess is that is an Aluminum Polymer capacitor with a value of 330uF at 2.5V. It’s the only type I can think of that comes in a can form with such a low operating voltage. Consider how your multimeter reads a resistance. It applies a DC voltage (or fixed current) across the probes and measures the current (or voltage across) through the device you’re measuring. What does a capacitor do to DC voltages? If your meter is capabile of measuring ESR, I wouldn’t be surprised if it has a “capacitance” mode that may let you measure it directly. Since the capacitor is rated for 2.5V, you have to be careful when measuring because there is a chance the meter may source a higher voltage than what the cap can tolerate.

  4. This part is most likely an Aluminum Electrolytic capacitor. Most of what I said about #3 is valid here too. It’s rated voltage is likely higher than #3.

-Bill

3

My multimeter is a Fluke 115 and I have a mesr 100 esr meter , regarding the diode for the first few seconds I get the numbers 1.000 and moves up and then stops and goes to OL and the same for backwards .

I am not sure if my multimeter or mesr 100 is capable but I did another reading on the the 3rd polymer capacitor, and put the multimeter in ohms setting and it read 3.000 ohms up to 4.500 and down a bit so not sure if that is normal, my esr meter reads 0.040 but to work out if the cap is good on the mesr 100 meter you have to refer to the chart which only goes from 10v min to 250v max .

4

phalanx:
Hi Katie,

Let’s go through what you’ve found so far.

  1. Inductors will generally be low resistance. I did a quick Digikey search for “2R2” inductors and 0.3 Ohms is in the realm of possibility for them. Depending on what you are using for a multimeter, you may not be able to accurately measure resistances that low. If you can’t find the part’s datasheet to see its specific properties, you may have to do more advanced testing to determine if the inductor is healthy.

  2. Think about the properties of a diode and what it does to DC voltages. With your meter in “Diode” mode, what happens if you measure the diode backwards (flip your probes to the opposite terminals)?

  3. My best guess is that is an Aluminum Polymer capacitor with a value of 330uF at 2.5V. It’s the only type I can think of that comes in a can form with such a low operating voltage. Consider how your multimeter reads a resistance. It applies a DC voltage (or fixed current) across the probes and measures the current (or voltage across) through the device you’re measuring. What does a capacitor do to DC voltages? If your meter is capabile of measuring ESR, I wouldn’t be surprised if it has a “capacitance” mode that may let you measure it directly. Since the capacitor is rated for 2.5V, you have to be careful when measuring because there is a chance the meter may source a higher voltage than what the cap can tolerate.

  4. This part is most likely an Aluminum Electrolytic capacitor. Most of what I said about #3 is valid here too. It’s rated voltage is likely higher than #3.

-Bill

I was using my multimeter on the wrong setting for measuring capacitance of them two caps , I now have it set on the - n f - auto , for the 3rd capacitor polymer I get 531 uf , the numbers fluctuate up and down in small amounts ,

4th Cap I get 70.0uf , only problem is the numbers are not the same as what is on the capacitor ,although I understand it can be ok for it to be a little out of range . what do you think?