Seiko 0903 only runs when very hot

[steve1811uk]

Hi, I have a Seiko 0903 that has issues oscillating. Trimmer capacitor was cracked and has been replaced with a fixed 22pF capacitor.

The watch will only run if I apply heat with a soldering iron on the connection between the IC and the crystal. After doing that the watch will run for about 5 minutes before the oscillator stops and the watch stops ticking.

After that happens the only thing that can get the watch going again is to apply heat with the soldering iron to the crystal legs/IC.

I have tried different capacitors in the range of 10pF to 27pF and that seems to have no effect on the oscillator stopping after 5 minutes after applying heat.

Any idea what is happening here? I suspect an issue with the quartz crystal or the IC. I have a new quartz crystal on order the 7 x 2mm cylinder style that I can give a try when it arrives. Just hoping it's not the IC.

Thanks in advance for any help here. Steve.

[watchweasol]

Hi have you checked for a dry joint when cold, the joint may be open circuit when cold.  If you can re solder the joint. Clean off and re do

[steve1811uk]

3 hours ago, watchweasol said:

Hi have you checked for a dry joint when cold, the joint may be open circuit when cold.  If you can re solder the joint. Clean off and re do

Thanks. I have resoldered it a couple of times with new solder and that's how I know that the heat from the soldering iron makes it work for a few minutes. I am thinking it must be something internal to the quartz crystal or the IC.

[watchweasol]

Yes. I think that’s the next port of call  if you can scavenge another crystal piggyback the original  one  just to prove the theory. Bergeron used to supply a crystal pen just to do that .  The pen consisted of a fancy tube with a crystal glued in the end . 

 

[steve1811uk]

With a little bit of help from Deepseek and some lateral thought I have fixed the issue and the watch is ticking reliably again.

I removed the quartz crystal and there was a lot of sticky crud between its metal case and the IC and also between the two closely spaced crystal terminals. I assume conductive hygroscopic remains of a battery leakage.

After cleaning thoroughly with water and pegwood then drying all is well. I assume that the heat from the soldering iron was drying out the conductive salts temporarily before they attracted moisture and conducted again causing energy loss from the oscillator eventually stopping it.

 

From Deepseek:

 

Yes, several of the compounds formed after a silver oxide battery leaks can **conduct electricity when wet**, especially if they dissolve in water or absorb moisture to form an ionic solution. Here's a breakdown:

 

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### **Compounds that Conduct Electricity When Wet:**

1. **Potassium hydroxide (KOH)** and **sodium hydroxide (NaOH)**:

   - These are strong electrolytes and highly conductive when dissolved in water. They dissociate into ions (K⁺/Na⁺ and OH⁻), which allow the solution to conduct electricity.

 

2. **Potassium carbonate (K₂CO₃)** and **sodium carbonate (Na₂CO₃)**:

   - These salts are also electrolytes. When dissolved in water, they dissociate into ions (K⁺/Na⁺ and CO₃²⁻), making the solution conductive.

 

3. **Potassium zincate (K₂ZnO₂)**:

   - This compound is soluble in water and dissociates into ions (K⁺ and ZnO₂²⁻), making it conductive when wet.

 

4. **Zinc hydroxide (Zn(OH)₂)**:

   - While zinc hydroxide is not very soluble in water, it can form a slightly conductive solution in the presence of moisture, especially if it reacts with acids or bases to form more soluble ions.

 

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### **Compounds that Do Not Conduct Electricity (or are Poor Conductors):**

1. **Silver oxide (Ag₂O)** and **silver carbonate (Ag₂CO₃)**:

   - These compounds are not very soluble in water and do not dissociate into ions easily. They are poor conductors of electricity, even when wet.

 

2. **Zinc oxide (ZnO)**:

   - Zinc oxide is insoluble in water and does not dissociate into ions, so it does not conduct electricity when wet.

 

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### **Why Conductivity Matters:**

If a silver oxide battery leaks and leaves behind residues of **KOH, NaOH, K₂CO₃, Na₂CO₃, or K₂ZnO₂**, these compounds can absorb moisture and form conductive pathways. This can lead to:

- **Short circuits** in electronic devices if the leakage occurs inside a device.

- **Corrosion** of metal contacts due to the conductive and corrosive nature of the residues.

 

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### **What to Do:**

If a battery leaks, it’s important to:

1. Clean the area thoroughly to remove all residues.

2. Use a mild acid (like vinegar) or a baking soda solution to neutralize any remaining alkaline compounds.

3. Dry the area completely to prevent further conductivity or corrosion.

 

Hope it helps.

Edited February 28 by steve1811uk