Hello.

Would like to ask if it's possible to identify a seemingly missing component from a small circuit board based on a photo with said component present?

I have attached 2 images which show the internals of a key fob that should work with old models of Ford Galaxy, Seat Alhambra, etc.
The key that I have seems to be missing one little diode? (marked in the yellow circle). As the key doesn't show any signs of life after 2 battery replacements, a closer inspection revealed this possible cause for it.

Unfortunately I have no idea what the possible specifications for this missing component could be.
All I know is that the chip itself is 'Siemens 977201b', and that the bigger metal plate like connector connect to a + side of a 3V button cell battery type CR2016, which there are 2 stacked on top of each other, thus sending 6V to the board if I'm not wrong?

The metal connector base seems to be in direct connection to the left side (looking at the image) of the missing component. If this helps in any way.

If it's possible to figure out the missing element and I could find it and make the key fob work, it would be easier than trying to find another fob as they are not easy to come by.

Thank you!

 

Welcome to AAC.

The diode may be a protective diode in case the battery is inserted reversed (upside down). It needs to pass the full current, which isn't much. It could be a Schottky diode to reduce voltage drop. I would try a 1N4148 (common) first (https://www.vishay.com/docs/81857/1n4148.pdf ). If that doesn't work, then a Schottky.

 

Hi.
Thank you for the advice.

I found a very similar looking (and size) diode inside some old electronics (phone charger). Soldered in place into the key fob.. and it works
Not sure if the diode is entirely correct as I don't have schematics, but it functions for now which is great.

Best regards!

 

BAT47 diode...