Alarm Remote PCB: identifying a missing component

Thread Starter

FiNaR

Joined Aug 4, 2018
17
Hi all,

I am new to the forum! I also need to admit that I am quite a newbie in the electronic world ;)

I have an home alarm Remote that is not working anymore, and after visually inspecting it, I have found out what is the problem: there is a missing component, probably felt off when I dropped the remote and if ended up "split in the ground"...

I have also a "working" remote, which I have opened to try to identify what is the "missing component"... unfortunately I am not so good with electronics, and I cannot see any writing on the "missing component...

Can anyone help me with this task? :D Please look at the attached file :)

Many thanks all
 

Attachments

ebp

Joined Feb 8, 2018
2,332
It is either an inductor or a capacitor. I can't tell for sure what color it is. If it is quite dark grey it is probably an inductor. If it is more of a brownish color it is probably a capacitor.

If you have a meter with small probes, you could try measuring the resistance between the ends of the good part, but be very careful not to mechanically damage it. Remove the battery for a few minutes before attempting the measurement. If it is an inductor the measured resistance will be low - likely a few hundred ohms at most. Higher than that probably means a capacitor, but that isn't really certain with the part in-circuit.

Unfortunately, whether it is an inductor or capacitor trying to guess the right value is nearly impossible. Surface mount capacitors almost never have the value marked and it is only a little more common for small SM inductors.
 

Thread Starter

FiNaR

Joined Aug 4, 2018
17
If it is quite dark grey it is probably an inductor. If it is more of a brownish color it is probably a capacitor.
It is dark grey... consider that it has more than 15 years, and built for an Italian alarm company (Logisty)... therefore, I am not sure if the color coding is still the same :(

If you have a meter with small probes, you could try measuring the resistance between the ends of the good part, but be very careful not to mechanically damage it.
I do not have small probes, I will definitely get them and see... as newbie, I am not sure what I should expect form the measurements...

  • if inductor, what I should get?
  • if capacitor, what should I get?
could it be a resistor? :rolleyes:
 

ebp

Joined Feb 8, 2018
2,332
If it's an inductor the resistance will be no more than a few tens of ohms. The DC resistance of a capacitor would be many megohms at minimum, but in-circuit it is hard to day what might be measured because there may be other current paths in parallel.

The colors I mentioned are the inherent colors of the materials used - nothing to do with coding. The ceramic materials of SM capacitors are usually white, light beige or tan - there are many on the board. The materials used for inductors are often dark grey, but SM inductors are quite variable in appearance.

The shape says it is extremely unlikely that it is a resistor. Wire wound surface mount resistors can have a square cross-section but would be much larger and a wirewound resistors has no place in low power circuitry. Film type resistors have a low-profile rectangular cross section and usually are marked.

It looks like one end of it connects to the battery. Since the other end does not connect to anything that looks like "ground" (as would a decoupling capacitor) this favors the idea of it being an inductor used to block high frequency. This would be a good thing, because it would mean the value would likely be non-critical.

If you only have big probes, try wrapping some bare solid copper wire around them to make small points, or use clip leads and sewing pins or the like.
 
Top