Author Topic: My new project  (Read 6476 times)

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Offline Mr J

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My new project
« on: February 05, 2011, 03:07:18 am »
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.
 

Offline Lance

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Re: My new project
« Reply #1 on: February 05, 2011, 04:35:19 am »
Score. How do crystals like that break? Was it just a shock that broke it?
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Offline Zero999

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Re: My new project
« Reply #2 on: February 05, 2011, 10:12:41 am »
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.
 

Offline Mr J

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Re: My new project
« Reply #3 on: February 05, 2011, 05:54:47 pm »
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.
 

Offline saturation

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Re: My new project
« Reply #4 on: February 05, 2011, 08:04:32 pm »
Nice.  The counter looks to be in good shape, and good job with your quick and accurate troubleshoot.
« Last Edit: February 06, 2011, 02:57:57 pm by saturation »
Best Wishes,

 Saturation
 

Offline Zero999

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Re: My new project
« Reply #5 on: February 06, 2011, 09:03:42 am »
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.
I'm surprised you had to order a custom made crystal and couldn't find a standard part. My local supplier sells 6.5536MHz although they're only 30ppm so not good enough for your application.
http://uk.farnell.com/iqd-frequency-products/lf-a135a/crystal-6-553600mhz/dp/9712348
 

Offline PStevenson

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Re: My new project
« Reply #6 on: February 10, 2011, 10:54:27 pm »

it makes me sick to the stomach when I know beautiful things like that can just get thrown away by people!
I got an old tiny 15MHz phillips oscilloscope in a similar way, it was just an internal fuse that had gone.
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Offline Mechatrommer

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Re: My new project
« Reply #7 on: February 11, 2011, 03:36:08 am »
it makes me sick to the stomach when...
thats what happened when you know too much ;)
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Offline PStevenson

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Re: My new project
« Reply #8 on: February 11, 2011, 09:20:22 am »

I just hope Darwin sorts those people out!
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Offline DavidJRobertson

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Re: My new project
« Reply #9 on: February 28, 2011, 08:39:47 pm »
... the sub-straight is really thin...
*substrate.
Sorry just crap spelling pisses me off.
 

Offline JohnS_AZ

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Re: My new project
« Reply #10 on: February 28, 2011, 09:44:54 pm »
... the sub-straight is really thin...
*substrate.
Sorry just crap spelling pisses me off.

[I'm] sorry [, it's] just [that] crap spelling pisses me off.

Spelling:       A
Grammar:      F
Punctuation:  F

 :)
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Offline DavidJRobertson

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Re: My new project
« Reply #11 on: February 28, 2011, 09:55:35 pm »
... the sub-straight is really thin...
*substrate.
Sorry just crap spelling pisses me off.

[I'm] sorry [, it's] just [that] crap spelling pisses me off.

Spelling:       A
Grammar:      F
Punctuation:  F

 :)
Haha good point.
 


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