Identify this Surface Mount Component

[Rofflesaur]

On today's episode of Name this Component:

What the heck is this?



I'm troubleshooting an RF receiver for an automotive RF keyless entry module. While checking various components on the board, I came across that. It looked like a fuse, so I tested continuity and there was none. It's so far on the back of the board and nowhere near where power enters, so what would a fuse be doing there? It appears to have the number 4.0 on it, and the area of the PCB where it sat was labeled "X1." Here's a pic of that...



Edit: This board is from 1997, so it may not be something that's used in modern designs.

[Mark]

Xtal

[Rofflesaur]

Xtal

In a glass MELF package? Is that a thing? Lol.

[DaJMasta]

Looks like it is, X is a crystal designation and it's got the load caps on either terminal, so I'd assume it's a 4MHz crystal.

[Rofflesaur]

I think you guys are correct. I didn't even know such a thing existed! I connected it back to the vehicle and probed the component with my DVM (don't have a portable scope). I very briefly saw 3.98Mhz before it crashed from the additional loading. I suppose I'll post in the RF sub forum tomorrow, as this is out of my area of expertise. Thanks.

[TimNJ]

It's a Murata CSAC series ceramic resonator.

https://www.rf-microwave.com/en/murata/csac4-00mgc/4-mhz-ceramic-resonator/rce-4m-a/