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Fitting new oscillator on an led board.

MyRetroWatches
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MyRetroWatches Member

MyRetroWatches

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Hi guys I am new here but hope perhaps you can help. I have a collection of 30 or so watches many of which are 70s retro mechanical , jump hour or now led.

I just love that genre.

Ok so I have a trafalgar led which is a lovely example and near mint contortion apart from the module. I found upon receipt that there had been a battery leak. However not as bad as I have seen and this module still would light. Randomly though. You would press a button and any digit would display at random , sometimes nothing.

I cleaned the board with a fibre pen, contact spray and a combination of water and baking soda to null the acidity. I then used my multimeter to test tracks that I could. I found all seemed to be working. I even tweaked the trimmer a little just to see. Sadly all this came to nothing and the module remains faulty.

I then researched online and found that this "could " be a bad / faulty oscillator. Common problem in led watches so I am told.

I have ordered a replacement one 32mhz in the hope that this might fix it.

 

Questions,

 

To you more experienced , does this sound like a oscillator problem?

 

How easy are they to fit?

I have a small tipped soldering iron , not that I'm any good but would try.

 

I read somewhere else of a guy suggesting to leave existing wires soldered to the board and to cut them higher up the stem to remove the old one. Then put the new one next to the short stems and solder together each side.

 

Does this sound plausible?

 

Any advise would be greatly received as I'm really Stuck here and want to at least attempt a fix.

 

The module is a

Mostek 03150-04

 

 

358176388df592aad8a8966fbb11756d.jpg

 

307106633815cc891d73c132a743f146.jpg

add0f1a8d606bb8189200937bb366d5c.jpg

 

 

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Spencelayh Member

Spencelayh

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Hi if you can get your hands on an oscilloscope you will be able to see if the oscillator is running by attaching to one of the crystal leads via a high impedance probe. Alternatively if you have already ordered the crystal try fitting it. If you are not confident of your soldering (desoldering) skills then it may be better to cut the leads and solder to the bit that is left although the result will not be as good a joint.

Phil

 

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Alastair WRT Addict

Alastair

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32MHz is wrong frequency I think......

32KHz is more usual for the Crystal of a watch. You cant replace the Oscillator circuit itself,--Thats part of the chip on the board, but can replace the crystal, which is the resonant component of the oscillator scheme. Be aware, Quartz Crystals are incredibly reliable though, usual mode of failure is loss of frequency over many years of use, but they still work....

More than likely, the batt leak has crept under that SMD chip and done damage, possibly both physically and internal to the chip electronically.

--Best get it off the board, but you'll need SMD rework skills and hot air gear to do it, plus the closeness of the LED's presents issues reworking this board!

 

BTW-- You cant neutralise an Alkalis using another Alkalis chemical such as sodium bicarb.. Watch battery 'acid' --Isnt acidic, Its Alkalis, ie, Caustic Soda or Potash based chemical compounds.

Dilute Vinegar would be a better choice!

Edited by Alastair
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MyRetroWatches Member

MyRetroWatches

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32MHz is wrong frequency I think......
32KHz is more usual for the Crystal of a watch. You cant replace the Oscillator circuit itself,--Thats part of the chip on the board, but can replace the crystal, which is the resonant component of the oscillator scheme. Be aware, Quartz Crystals are incredibly reliable though, usual mode of failure is loss of frequency over many years of use, but they still work....
More than likely, the batt leak has crept under that SMD chip and done damage, possibly both physically and internal to the chip electronically.
--Best get it off the board, but you'll need SMD rework skills and hot air gear to do it, plus the closeness of the LED's presents issues reworking this board!
 
BTW-- You cant neutralise an Alkalis using another Alkalis chemical such as sodium bicarb.. Watch battery 'acid' --Isnt acidic, Its Alkalis, ie, Caustic Soda or Potash based chemical compounds.
Dilute Vinegar would be a better choice!


Thank you sir, reading posts about led watches often symptoms of bad crystal is random leds hence why I wanted to try. As for frequency I chose 32 based on what it says on the underside of the crystal MTQ32A . I couldn't find much googling this.
I am hoping that the crystal is not working right for the chip not to decode right.
I want to give it a go as the alternative is to find a donor module from another watch. I am actively looking but for the sake of trying its worth having a go.
You sir sound like you know what your taking about and I have taken on board your help so thank you for that.

As for the bicarbonate your right I just thought it might help. I did also use some white vinegar on a Q tip on the copper contacts which worked well.

Battery damage looked quite recent to be honest, I've seen allot worse.

Again thank you for taking the time to reply. Appreciated.


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MyRetroWatches Member

MyRetroWatches

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Hi if you can get your hands on an oscilloscope you will be able to see if the oscillator is running by attaching to one of the crystal leads via a high impedance probe. Alternatively if you have already ordered the crystal try fitting it. If you are not confident of your soldering (desoldering) skills then it may be better to cut the leads and solder to the bit that is left although the result will not be as good a joint.
Phil
 

Thank you sir. Appreciate your reply.
I can't get hold of an oscilloscope. I have soldered boards but not small watch boards as this. I will try to join first, if it solves the issue I know I just have to make joins better or pay someone to make good .

Thanks


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