Electric circuit cleaning

[Khan]

Hi

Is it too late to save a watch such corroded from an old battery? If it can be cleaned, how to do so? I tried to remove the blue corrosion with pegwood and rodico but the watch still doesnt work. Its a 90s 6m15 Seiko movement. 

[HectorLooi]

I usually clean battery leaks with white vinegar. Use a brush or cotton bud and dab the vinegar all over the corroded parts. Let it soak for about 5 minutes, then rinse with distilled water. Sometimes the battery juice (potassium hydroxide) gets soaked into the substrate of the circuit board and causes a short. Other times, it eats away all the copper of the pcb track. 

After the board has dried, use a multimeter in resistance mode and test for continuity of the copper tracks and then for shorts between adjacent tracks. Test the battery contacts very carefully. Sometimes they may look clean but there can be corrosion under the rivets and have several hundred ohms of resistance.

If everything looks good, then put a battery in and test that it gives a pulse on the pulse meter. I would also test the current consumption with a microammeter but that is not a tool that most hobbyist have.

[Khan]

Thank you for the great explanation. I just added an "after" picture of the circuit. Haven't cleaned with vinegar yet but in the meanwhile, I removed the top of corrosion "bricks" with a screwdriver just to brake the blue corrosion but at one place it took the green coating of one of the copper tracks away and in some areas done light scratches, does that make any harm? 

I unfortunately have none of the instruments. How can I know if the coils are faulty? 

Im talking about this area

[Neverenoughwatches]

8 hours ago, Khan said:

Thank you for the great explanation. I just added an "after" picture of the circuit. Haven't cleaned with vinegar yet but in the meanwhile, I removed the top of corrosion "bricks" with a screwdriver just to brake the blue corrosion but at one place it took the green coating of one of the copper tracks away and in some areas done light scratches, does that make any harm? 

I unfortunately have none of the instruments. How can I know if the coils are faulty? 

Im talking about this area

You will need a resistance meter to check for continuity of the coil windings, a very cheap piece of equipment. Battery leaks are the main cause of damage in quartz movements. One must always replace the battery once its energy has been used up, the battery case then becomes it's food, then the movement.  Pulling out the crown to hack the watch will prolong the battery life.

[JohnR725]

8 hours ago, Khan said:

I unfortunately have none of the instruments.

one of the unfortunate problem with watch repair is the slow accumulation of tools sometimes expensive tools. then with electrical watches you end up with more tools some of which can be dreadfully expensive but others could be insanely cheap. For instance at work I have a $20 digital volt meter that I purchased a very long time ago. It works really well for checking resistance, continuity through the circuits and battery voltage. then it's really nice if you have pointy test probes with fine tips as everything the watch requires something smaller.

 

9 hours ago, HectorLooi said:

Test the battery contacts

if the watch has a battery strap holding the battery in place then it's nice to connect test probes to worthy fool to where the power is going to verify it's actually going there at all. Often times people forget the but the insulator in at shorts the battery out other times contacts are quite where there supposed to be in nothing goes through it all. Unfortunately with electric watches you do need some test equipment to test as you can't look and see the electricity flowing.

 

[Khan]

Ok now I got a multi meter and cleaned the circuit board and battery contacts with baking soda/pegwood and rinsed them in isopropyl alcohol. As you see, two copper dots seems damaged (The multi meter gives no response when the black probe on the + sign and the red probe on those two cobber dots).

When I assemble everything together, there is again no response when the red probe is on minus and black probe close to the + sign. But when I move the red needle to the green circle then there is response on the multi meter! Anybody know what could be wrong? 

I also checked those four coils individually and there seem to be life shown on the multi meter as well. 

Edited March 2 by Khan

[watchweasol]

Hi khan. Where the tracks have been destroyed it may be possible ti re connect them using conductive paint to bridge the gaps. The same stuff used in repairing car window heaters and larger circuit boards. Can be used to repair scuffed coils.

[HectorLooi]

There is a screw missing in the green circle. Without it, the (-) terminal is not making proper contact with the circuit board.

[Khan]

Oh, the batteri is fixed with the clamp and two screws as shown. By the way, I didnt disassembled the minus port when cleaning, should I do that? The one im checking with the red probe. 

49 minutes ago, watchweasol said:

Hi khan. Where the tracks have been destroyed it may be possible ti re connect them using conductive paint to bridge the gaps. The same stuff used in repairing car window heaters and larger circuit boards. Can be used to repair scuffed coils.

Hi

Can a single destroyed track make a watch not run at all or can it run with functions working partially? 

Edited March 2 by Khan

[HectorLooi]

2 hours ago, Khan said:

cleaned the circuit board and battery contacts with baking soda/pegwood and rinsed them in isopropyl alcohol

You did not follow my instructions.

 

1 hour ago, Khan said:

Can a single destroyed track make a watch not run at all or can it run with functions working partially? 

Depends on where the break occurs. It's just like your house electrical wiring. If the wire to your fridge is broken, only the fridge doesn't work. But if the main wire supplying the whole house is broken, then everything doesn't work.

The design of this watch has a screw going through the (+) battery clip and through the (-) battery terminal. You have to make sure that the insulator keeping the 2 apart is placed properly and there is no short circuit.

[Khan]

On 3/3/2024 at 1:09 AM, HectorLooi said:

You did not follow my instructions.

 

Depends on where the break occurs. It's just like your house electrical wiring. If the wire to your fridge is broken, only the fridge doesn't work. But if the main wire supplying the whole house is broken, then everything doesn't work.

The design of this watch has a screw going through the (+) battery clip and through the (-) battery terminal. You have to make sure that the insulator keeping the 2 apart is placed properly and there is no short circuit.

I have now cleaned the circuit board in white vinegar and rinsed in destilled water due to your instructions. Furthermore, the broken gaps are now filled with conductive paint. And now there is reaction on the multimeter when the red probe at the green arrow and the black probe on the + sign. And when I assemble everything together, there is reaction in the battery clip as well, BUT the watch is still not working. How can that be? 

[watchweasol]

Hi Khan. Before proceeding make a thorough check of the repaired areas to be sure you are not bridging tracks and causing short circuits as some look a bit rough. Then assemble the watch and  fit battery or use a1.55v supply connected to the    Plus +. And Minus - contacts   The contact points for the supply with the meter to verify the power is reaching the circuit board  and reaching the CMOS. Chip  then check each coil with the meter for a pulse. If your meter will allow you to with  micro amps scale. Some meters don’t go as low as that.  Checking the circuit board without proper instruments is not easy (oscilloscope)  and meters. If the CMOS is not getting power it will not work.and will not pulse the coils and the rotor. The attached below will help you understand the quartz watch a little better.   Cheers.

Witschi Training Course.pdf

[HectorLooi]

This spot here looks like the conductive paint is shorting out a few tracks. 

As this is a double sided pcb, things become a lot more complicated because of "through hole vias".  This means that the holes have copper in them that connect one side of the pcb to the other. You'll have to check for continuity on one side to the other side wherever there is a hole.

There is still the possibility that the IC itself is damaged.

[Khan]

1 hour ago, HectorLooi said:

This spot here looks like the conductive paint is shorting out a few tracks. 

As this is a double sided pcb, things become a lot more complicated because of "through hole vias".  This means that the holes have copper in them that connect one side of the pcb to the other. You'll have to check for continuity on one side to the other side wherever there is a hole.

There is still the possibility that the IC itself is damaged.

I tried to re-paint the area by using a needle to move the paint from the pen. Now the tracks should'nt be joined. I figured out that one of coil seems damaged(the one with green arrows). Can this cause the watch to not work at all? 

By the way, the number I get on the multimeter for the square cobber area for battery insulator, is 0.07 when multimeter turned on (omega 200). Is that too low? 

[HectorLooi]

2 hours ago, Khan said:

By the way, the number I get on the multimeter for the square cobber area for battery insulator, is 0.07 when multimeter turned on (omega 200). Is that too low? 

I'm sorry, I don't understand this part. Can you indicate the points you tested on the photo.

[watchweasol]

Hi Khan if you haven’t got the technical document I have enclosed it for you

 

if you put a meter on the ohms range and short the points you will get full scale deflection. So likewise if you place the probes on a wire coil if the coil is intact get the same if no reading at all the coil is said to be open circuit,  a break in the wire ,  it is conceivable that the  CMOS is dead that’s why you need to verify the circuit is getting power.

6M15A&6M91A.pdf

[Khan]

6 hours ago, HectorLooi said:

I'm sorry, I don't understand this part. Can you indicate the points you tested on the photo.

As on photo here 

[watchweasol]

Hi I have attached another book which might help.   On your circuit board there is a pad marked. Plus. +.    And next to it is another marked minus.  -   Theses two pads are the power input to the board, without the right tools diagnosis of the board on its own is very difficult.  In its disassembled state all you can check is the coils and visually check the tracks on the board. To check the board on its own requires a power source, a load and probably an oscilloscope plus circuit diagram.  Have a read of the attachment as it outlines quartz watch workings ant testing equipment and meter usage and understanding.

ElectricWatchRepairManual.pdf

[Khan]

Hi

Some questions

I wonder why none of the tracks with conductive paint gives result on the multimeter. Does the paint loose its "connectivity" if I first apply the paint on an oil-pen and then on the circuit board? I have assured that the tracks are not bridged with paint. 

One of the coils seems damaged according to the multimeter but the coil looks intact in the loop. The end of the coil initially had some battery juice on it adjacent to the old battery. 

 

 

[JohnR725]

3 hours ago, Khan said:

One of the coils seems damaged according to the multimeter but the coil looks intact in the loop.

the unfortunate problem of most electronic things are visually they can look outstanding and no longer be functional at all. Which is why you need a electronic test equipment to verify that they still have whatever electrical properties there supposed to have.

[rjenkinsgb]

That conductive paint just does not look good. it looks like separate particles rather than a solid conductor.

The better types are silver based, but even those are not guaranteed to work if the conductors they join to are not immaculately clean & the stuff applied perfectly.

Do you know anyone who works on electronics professionally? They should be able to bridge the broken track sections with bits of fine wire soldered in place.