An ice cube maker stopped working with the symptom that the temperature cycles are getting shorter and shorter.

I suspect that the microcontrollers clock is not working properly.

I desoldered a part near the clock and I want to replace it.

This is the part in question.

It is labeled '4.00 J'. I can not identify the part and google did not put out useful information for me.

This is where I desoldered it from.

The microcontroller is this one, page 19 shows its pins. The XT component center pin (pin 2) is connected to vss. XT pin 1 os connected to XIN/P1.0. XT pin 3 is connected to XOUT/P1.1.

Most confusing for me is that the XT component has a 'J' printed on it. What does that label mean and what could be my unknown XT component?

  • 2
    \$\begingroup\$ Looks like a ceramic resonator: en.wikipedia.org/wiki/Ceramic_resonator. Probably 4 Mhz. You can probably replace it with a 4 Mhz crystal directly in circuit, and it should work. \$\endgroup\$
    – Zuofu
    Apr 19, 2015 at 11:29
  • \$\begingroup\$ @Zuofu thanks for the comment. Why would that component be labeled 'J' instead of 'M' though? \$\endgroup\$
    – raschmugl
    Apr 19, 2015 at 11:32
  • \$\begingroup\$ No clue, maybe a temperature/grade code... \$\endgroup\$
    – Zuofu
    Apr 19, 2015 at 11:33
  • \$\begingroup\$ The label 'J' is most probably the tolerance designation, and in that case means 5%. \$\endgroup\$ Apr 19, 2015 at 11:39
  • 4
    \$\begingroup\$ @Zuofu: No, you can't replace that with a crystal. Crystals are just bare crystals, meaning 2-pin parts. That's a 3-pin part with the load caps built in. \$\endgroup\$ Apr 19, 2015 at 11:40

1 Answer 1


That is a ceramic resonator. It is electrically similar to a quartz crystal, although less accurate. The advantages of resonators over crystals are that they are cheaper, more mechanically robust, and usually require lower drive power. The 3-pin variety comes with the load caps built in.

The "4.00" may mean 4 MHz. The "J" is probably a accuracy or temperature or package code the manufacturer uses in the part number. Check if Murata has something similar.

  • \$\begingroup\$ If you have a pile of scrap floppy drives, check them ... they often have that kind of part in them.... \$\endgroup\$ Jun 7, 2018 at 13:10

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