Litronix 'eats'crystals - is it me ?

[james_stan]

Hi All

If you have read any of my previous posts you will see I have been
trying to learn bits on a couple of litronix modules.

One has exposed bond wires so I guess after my ham-fisted effort at replacing the crystal it is b*ggered. Will no even show the 32KHz.

The other is stranger. On three occassions now I have replaced the crystal and it will start to work. I can 'scope the crystal and see 32 KHz. I can then short the cotnrol and set buttons to 3 Volts and
the LEDS come on and I can increment digits etc. (although I could still use a Litronix setting guide). I am powering the units using the 3v supply from a battery carrier (2 xAA) and two croc clips.

However if I leave the unit alone power disconnected and try again after a short break zippo ! On the crystal this time I could only register a flast 1.5ish Volt no 32KHz !

Is it so easy to break these crystals ?

Will they cook if the legs short with power-on ? Is it likely that the module itslef is inflicting the damage or is it simply my restrictive abilities ?

Yours frustratedly

James

[retroleds]

James:
You have a couple of things going on, possibly. First, most of the Litronix use a 32k crystal, but it was a three lead one - the third lead charged the crystal to get it "fired-up"('m using laymen's visuals here, electrical engineer types don't chew my head of f). The crystals were made by Statek Corp., their design had a larger piece of crystal(easier to handle) but required that "jump start". Your standard two lead crystals won't work, unfortunately, which is why I personally have abandoned buying Litronix items, and are selling off the few I have left.

Guy Ball(former owner of www.ledwatches.net) has a neighbor who works for Statek - I sold the man some parts for his HP calc. and he tried to help me by sending some of their more modern 32K crystals. Two lead, useless except in a very few of the very last modules Litronix made.

Regarding the soldering of crystals - if you are not using a heat sink between the solder point and the crystal, you are probably damaging them greatly. This is a few years old but a decent starting point on that topic. http://www.thedigitalwatch.com/Archives/QuickTip_002.htm
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[james_stan]

Hi Ed

Thanks for the informative reply. In the modules I have I only see
two nodes for connecting the crystal, also the 'square' ones I removed only had two leads so maybe I have modules of the later type to which you refer ?

I did read a bit about sinking the heat when replacing crystals but chose to ignore it (no fool like an old fool right ?) - when I saw the things initially working I convinced myself I was right...

.. I'll try one more crystal with a heat sink attached and see how we go.

BTW during all this I did think about making up a crystal testing circuit. You need some caps (20pF) resistors (100k, 10M) and a cmnos inverter apparently. I thought if the output is connected to a couple of LEDs (one in each direction) an oscillating signal will light-up both = pass. Anyone else tried this to save transplanting dead crystals.


Cheers

james

[retroleds]

[james_stan]