How to test Crystal Oscillators M1280 , 4 pins

Thread Starter

harrison2015

Joined Apr 22, 2015
80
How do you test these big silver square 12MHz, 25Mhz, 8Mhz crystal oscillators M1280, 4 pins?

How do you know if its good or bad? Is the only way to test a crystal oscillator is to apply voltage across it? I have removed the crystal oscillator out of the circuit. How can i set up an external power supply and monitor the crystals oscillators waveform using an oscilloscope?
 

Reloadron

Joined Jan 15, 2015
6,324
First you get the data sheet and look at the data sheet. Normally there is no reason to remove the crystal oscillator to test it. If you have removed it then just externally power it, while powered look at the output pin with a scope. Note I did not study your particular oscillator, some use a fourth pin as an enable pin which must be high for operation, not all but some. To test the oscillator in circuit just measure the output pin with a scope. If you do not have a scope you can try using an electronic counter. Either way, scope and counter need setup correctly. Scope ground goes to the oscillator ground with power ground.

See page 3 of the data sheet I linked to. Also, while they suggest a FET probe (very high impedance) I have done fine using a X10 probe with the 10 MegOhm input impedance.

Ron
 

#12

Joined Nov 30, 2010
18,223
Pretty much what Ron said: Find the part number, find the datasheet, read the datasheet, build the circuit that the crystal is supposed to be in, use an oscilloscope or frequency counter to see if it is running.

You can set up a power supply by buying one or building one, then attach it as the datasheet tells you. To, "monitor the crystal's oscillators waveform", you attach the oscilloscope probe to the output of the oscillator.
 

Thread Starter

harrison2015

Joined Apr 22, 2015
80
Normally there is no reason to remove the crystal oscillator to test it. If you have removed it then just externally power it

What should I set the current limit to on the external power supply?

Is there anyway I have damage the crystal oscillator?

while they suggest a FET probe (very high impedance) I have done fine using a X10 probe with the 10 MegOhm input impedance.
Why would I need a FET probe?
You want me to solder a 10 meg ohm resistor on the tip of the oscilloscope probe?
 

Thread Starter

harrison2015

Joined Apr 22, 2015
80
Normally there is no reason to remove the crystal oscillator to test it. If you have removed it then just externally power it

What should I set the current limit to on the external power supply?

Is there anyway I have damage the crystal oscillator?

while they suggest a FET probe (very high impedance) I have done fine using a X10 probe with the 10 MegOhm input impedance.
Why would I need a FET probe?
You want me to solder a 10 meg ohm resistor on the tip of the oscilloscope probe?
 

Thread Starter

harrison2015

Joined Apr 22, 2015
80
Do you think its better to use a frequency counter instead of an oscilloscope? But the test circuit wants us to look at the waveshape of the crystal oscillator.
 

Reloadron

Joined Jan 15, 2015
6,324
Back in post #2 I gave you a link to the data sheet, including the test circuit.

Setting the current limit on the test power supply matters not. These devices do not draw over 100 mA and the device will only draw the current it needs. I haven't any idea if you damaged it removing it. The only way to damage it would be excessive heat or literally dropping it hard enough to crack or break the crystal. Using a scope is adequate for testing it, you only need a counter to accurately measure the frequency.

This is or should be simple so do not make it complicated. Use a scope and look at the output waveform.

Ron
 

debe

Joined Sep 21, 2010
1,273
Heres a picture of one cut open & ive tested them just by probing the OP pin with out a load using a cro probe on X10. Ive salvaged heaps of these of a wide range of frequencies.XTAL OSC.1.JPG XTAL OSC.2.JPG
 

Thread Starter

harrison2015

Joined Apr 22, 2015
80
Do these types of crystal oscillators ever go bad? like change its waveform shape or change its frequency? They are from the 80's and 90's
 

Reloadron

Joined Jan 15, 2015
6,324
Do these types of crystal oscillators ever go bad? like change its waveform shape or change its frequency? They are from the 80's and 90's
Thinking back, way back and don't ever remember seeing one fail. That is not to say they never go bad or drift, just to say I don't remember a failed one.

@debe, nice pictures.

Ron
 

wayneh

Joined Sep 9, 2010
17,160
Just throwing this out - if you have a radio receiver that can tune to the relevant frequency, you should be able to detect the oscillator. Use a length of wire on the output as your transmitter antenna. I've done this at 1MHz, which is on the traditional AM band. Not sure what would happen at those higher frequencies.
 
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