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My new project

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Mr J:
Found a old Simpson 710 Frequency Counter in the trash bin at work. Brought it home powered up okay but it was stuck on one frequency. After opening it up I heard a rattle from the crystal in the back. Tested the ICM7207 IC the crystal was connected to and zippo on the output, I took the crystal out and took it apart, bingo broken crystal. Have a new +/- 10ppm on order, hope it works.

What a great little unit from the 80's all though hole 74 series logic, small for the day. Still small today.

Score. How do crystals like that break? Was it just a shock that broke it?

It looks like it.

I've never experienced it myself but I've heard crystals can break like that if handled roughly and overvoltage at the resonant frequency will probably cause it to shatter in a similar manner.

Mr J:
yea I think it was shock that broke it, there is a bit of a dent in the corner of the housing and the crystal is right on the edge of the pcb. It's a fairly high frequency fundamental 6.553600 Mhz and the sub-straight is really thin. I order a custom one at ICM, mil spec made it thicker.

Nice.  The counter looks to be in good shape, and good job with your quick and accurate troubleshoot.


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