GM300 with leaky crystal

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GM300 with leaky crystal

Postby pks » Fri Feb 25, 2011 1:32 am

Recently decided to power up my GM300 that has been in storage for some time and noticed it would not RX any signals. Opened it up and noticed the 44.645Mhz crystal had yellow liquid oozing from its base and solidified. This yellow liquid has made contact with a few nearby SMD components. Is this liquid corrosive like the Spectra capacitors?
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Re: GM300 with leaky crystal

Postby Al » Fri Feb 25, 2011 10:01 am

Crystals are not filled with anything except perhaps dry nitrogen when they're hermetically sealed. Any kind of liquid or solid would not allow the quartz to vibrate. Likely what you're seeing is a drop of adhesive that was applied to the crystal case after board assembly to prevent the crystal's moving and stressing the leads/solder joints on the leads.
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Re: GM300 with leaky crystal

Postby wavetar » Fri Feb 25, 2011 10:23 am

Al wrote:Crystals are not filled with anything except perhaps dry nitrogen when they're hermetically sealed. Any kind of liquid or solid would not allow the quartz to vibrate. Likely what you're seeing is a drop of adhesive that was applied to the crystal case after board assembly to prevent the crystal's moving and stressing the leads/solder joints on the leads.


Seconded. It is glue as Al says. That said, it is very likely the crystal has gone bad if you're not receiving at all.
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Re: GM300 with leaky crystal

Postby Will » Fri Feb 25, 2011 12:34 pm

wavetar wrote:
Al wrote:Crystals are not filled with anything except perhaps dry nitrogen when they're hermetically sealed. Any kind of liquid or solid would not allow the quartz to vibrate. Likely what you're seeing is a drop of adhesive that was applied to the crystal case after board assembly to prevent the crystal's moving and stressing the leads/solder joints on the leads.


Seconded. It is glue as Al says. That said, it is very likely the crystal has gone bad if you're not receiving at all.



Correct, the second oscillator crystal may have gone weak and it does not oscillate anymore. A very common problem in older Maxtracs, Radius, and GM series mobile radios radios.

A quick test: tune your scanner to 44.645 mHz and listen for the carrier. You may have to remove the shield from the RF board in your GM300.

Motorola has changed the part number for the replacement second oscillator crystal. 4880606B02
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Re: GM300 with leaky crystal

Postby pks » Fri Feb 25, 2011 1:25 pm

What's the safest and easiest way to remove the glue before I attempt to desolder the crystal?
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Re: GM300 with leaky crystal

Postby Bat2way » Fri Feb 25, 2011 7:23 pm

Just use the tip of a mini-flat bladed screwdriver. Carefully pry a bit of the brown glue up and the rest will pull away enough to unsolder the crystal.
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