Hi, I was repairing a pair of Bluetooth in ear headphones and noticed after a lot of visual checking that one component was missing, there were marks of a soldered componente but the component was not still there. Probably a capacitor or resistor. Here are the pictures:



And a closeup:


I believe that is the reason the PCB without that component is not powering on, if anyone can confirm or guess that as well would fine fine to check it against other's opinions.

Now, the problem is I wouldn't like to mess with the perfectly fine PCB, so that's why I ask if there's any chance I can get the specs of that component without desoldering it. I would like to know as well if it has a fixed position (meaning a + and a - like many capacitors have). In case I have to desolder it I would like to know this info. I guess you can't tell if it's a capacitor or a resister by the color, right?

PD: the black cable is there because I broke accidentally the pad of one spot and I had to join one leg to an alternative spot, that one.

 

You can use an LCR meter or DMM to try and measure it in-circuit. You might not get a good result but you certainly should be able to tell if it is a cap, resistor, or diode.

It would be wild speculation to say one way or another without some idea of what the circuit looks like.

 

Measure the resistance across the mystery component, both ways.

 

But measuring the resistance will give me values of that component and all of the ones that are in parallel.

So you can't tell even if it's a cap or resistor?

 

But measuring the resistance will give me values of that component and all of the ones that are in parallel.

So you can't tell even if it's a cap or resistor?

Of course. But you said that you didn’t want to removed the component.
Measuring the resistance in-circuit will provide you with one clue without having to remove it.

 

Guys I don't understand...

I finally desoldered it, and my DMM is reading both ways:
0.6-0.7 Ohm
which is absurdly low I think.

If I read the Farads, it gives me all around 0.02nF up to 1.63nF, very, very inconsistent readings.

So what is it?

The component is so freaking small as well, even my smallest soldering tip is still way too big to work comfortably. I think you need a needle like tip to do this correctly and of course glasses for augmentation.

 

So, assuming the component is working correctly then is either a resistor or an inductor.
Can you measure low values of inductance?

 

Yeah, after an agonizing whole hour trying to get it out and put it on the broken PCB, it finally worked and now it turns on. My God I have absolutely never worked with such small pieces, and it's been really stressful, taking care not to invade other pads, the iron tip is as big as the whole component... Jesus, what kind of equipment do you guys use to work with such small things?

Anyways it's working now, both headphones get connected and now I'm upgrading the firmware of both.

Now... I want to buy this component again to put it on the PCB I removed it from, but the data is that I shared, both ways in both cases, a resistance of 0.5-0.7 ohm (actually my DMM has 0.0-0.3 ohm reading when the probes are touching each other), so it perfectly could be a 400 mOhm resistor. Is that an odd value?

About being a cap... The values were all around the place.

 

the iron tip is as big as the whole component... Jesus, what kind of equipment do you guys use to work with such small things?

Hot air tool and solder paste. If you can't get the air flow low enough, it helps to have a jig to hold the component down.

 

So what can I do?

I know that the whole thing won't turn on without that component, so I assume it must be a resistor, because I think a R can have such dramatic effect while a cap or coil couldn't. Could it be a 0.4 Ohm resistor?


Something like that?

Unfortunately I moved that component from one PCB to the one I wanted to repair, which I successfully did, but now I want to put the component in the other one. I don't have a L reader, my DMM only reads R or C.