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pcb componets home work help

dazzzer30

New Member
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
.
2. 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.

4. 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 .

<a href="https://imgur.com/SXY69rq">
 

rjenkinsgb

Well-Known Member
Most Helpful Member
An inductor just shows the resistance of the coil wire or trace at DC, and a very low resistance is not unusual with some types.
Commonly the higher the current they are rated for, the lower the DC resistance to minimise resistive power losses.

A good diode should show open circuit in one direction and continuity with a voltage drop (often around 0.6V) in the other direction.
It may give a reading on a resistance test but that depends on the meter. You may need to use a specific "diode test" range to get a sensible result.

With capacitors, there is nothing wrong with the values you give. Low ESR is good!
The other important value is the actual capacitance they measure at, which you have not given.

Also, any obvious visual defects, such as leakage or the casing starting to swell. #3 looks as if the top is bulging slightly?
If all of that style are the same, it may not mean anything - but if others have flat tops, it's probably an indication the cap is degrading.
 

dazzzer30

New Member
An inductor just shows the resistance of the coil wire or trace at DC, and a very low resistance is not unusual with some types.
Commonly the higher the current they are rated for, the lower the DC resistance to minimise resistive power losses.

A good diode should show open circuit in one direction and continuity with a voltage drop (often around 0.6V) in the other direction.
It may give a reading on a resistance test but that depends on the meter. You may need to use a specific "diode test" range to get a sensible result.
ho
With capacitors, there is nothing wrong with the values you give. Low ESR is good!
The other important value is the actual capacitance they measure at, which you have not given.

Also, any obvious visual defects, such as leakage or the casing starting to swell. #3 looks as if the top is bulging slightly?
If all of that style are the same, it may not mean anything - but if others have flat tops, it's probably an indication the cap is degrading.
yes you are right I did need to measure the Capacitance ! now I have my fluke 115 multimeter set to - n f - auto mode for the 3rd cap, it reads 472 uf - if I am correct the cap is rated 330 uf at 2.5v , I know the readings of uf can be slightly higher than what is rated on the capacitor and it can still be good , but how much more I do not know , so its only a guess but I have put the 3rd capacitor as good .

4th - capacitor is reading of 69.9 uf on multimeter , the number on the capacitor says 68 - 4A 6 so I am going to say this is 68uf rated , if its 68 uf then I will say the cap looks very good much of a close reading to the last one .

My esr meter is an mesr 100, I have not used it much yet , not sure it works with all caps this small or smaller because you have to take the reading and then go to the chat to work out if the cap is good , But the chart has 9 difference uf settings starting from min 10uf and 10000uk max , and then 7 different voltages settings starting with 10v up to 250v , I think both of theses caps i have are under 10v so i cant go by the chart to see the result , but i do a agree it would be a low reading on the esr meter .
 

Pommie

Well-Known Member
Most Helpful Member
Your second picture does not indicate any polarity, if it doesn't have a polarity indication then it's unlikely to be a diode.

Mike.
 

dazzzer30

New Member
Your second picture does not indicate any polarity, if it doesn't have a polarity indication then it's unlikely to be a diode.

Mike.
Thank you for point that out, I don't know why I didn't check this but I now think this is another capacitor , The picture does not pick this up but it has on it 470 46EP1 d . there is also a small shaded edge so i think this is negative side. so maybe 470 is uf not sure about the voltage rating , So i checked it for Capacitance and it shows 422 uf .

I also did a Continuity test and found something strange , when testing i heard beeps for about 10 seconds I think I had pos and neg from multimeter to pos and neg on capacitor ,so i tried again and there was no beeps , but i noticed when changing over leads positions from pos to neg on to the capacitor seems to make it beep for about 10 second , is this normal ?
 
Last edited:

rjenkinsgb

Well-Known Member
Most Helpful Member
A meter on a resistance range will momentarily see a large capacitor as a short circuit.

With one that has a continuity beep, if the capacitor is large enough so the charge time keeps the probe voltage low in the continuity trigger range for some time, it will beep until the cap charges sufficiently.

If the cap has already been connected the opposite polarity, it will take rather longer as it has to discharge first then charge at the new polarity.

If the cap is leaky when connected reversed, that may also show as continuity?
 

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