Citizen 8945 circuit board repair

[AndyHull]

BTW Have you checked the board under the microscope for cracks? These little PCBs have a hard life, and may be subject to heavy impacts, so they may suffer from hairline fractures.

EDIT2: Also check the tracks round any holes that may be subject to rubbing from plastic or metal fasteners. As you can see these are pretty small and thin tracks, so it doesn't take much friction to wear through them. Its difficult to tell from the pictures, but there are a couple of places like the one I have circled that look a little suspect.

Edited October 2, 2020 by AndyHull

[gkmaia]

14 minutes ago, AndyHull said:

BTW Have you checked the board under the microscope for cracks? These little PCBs have a hard life, and may be subject to heavy impacts, so they may suffer from hairline fractures.

EDIT2: Also check the tracks round any holes that may be subject to rubbing from plastic or metal fasteners. As you can see these are pretty small anda thin tracks, so it doesn't take much friction to wear through them.

Yes I did under 150x mag. No cracks. All the hole vias have continuity.

[HectorLooi]

Did you try putting it back in the movement and screw down everything. Some sneaky designs use the metal screws to power or ground another section of the board.

Also, watches with the "hacking" function have a switch that activates the circuit only when the crown is pushed in.

[JohnR725]

16 hours ago, gkmaia said:

Interesting as the positive is the chassis. Never seen that. There must be a reason, something to do with the charge of the human body as it is in contact with it permanently

I suspect the reason for a positive ground as I would call it is that the battery case is the positive.  it makes it easier to manufacture than the battery can go in and make contact with the metal somewhere you only need a insulated contact for the negative part.

one of things you should probably do is look at the service manual carefully and see if there's any reference to? Okay they do not expect you to run the circuits without being in the watch some quartz watches conceivably will have more than one ground screw as they call them. Or it's conceivable that there may be more than one connection for the power and/or ground.

typically in a quartz watch the quartz crystals should always be oscillating. Initially when their manufactured they need a time to stabilize and allowing the watch to run basically from the instant it's manufactured until it's given to the customer helps with that stabilization. This is why analog watches will often be in the setting position so it's not driving the stepping motor it saves power. But the quartz crystal as oscillating. Then I have a link below company that manufactures quartz crystals for timepieces.

https://www.microcrystal.com/en/products/khz-quartz-crystals/

 

[gkmaia]

i will check but from my first photo the red dots are the the positive rail and the tail dots are the negative. there is no jumper so they are probably all connected.

i building a little oscillator circuit for small capacitance and low frequency crystals. See if that helps getting better signals from these crystals.

 

[AndyHull]

A couple of cmos inverters from say a 74HC04 hex inverter or a CD40106 should be all you need to get a good clean square wave from one of those watch crystals.

There are a bunch of schematics on line for this.

You could go old school and use a CMOS 555 without the crystal or even a single transistor or two transistors (with or without the crystal) as an oscillator just for testing.

Just be careful to keep the signal level reasonably weak and commoned  to and  at or below the supply voltage of the board so you don't cook anything.

[gkmaia]

15 hours ago, AndyHull said:

A couple of cmos inverters from say a 74HC04 hex inverter or a CD40106 should be all you need to get a good clean square wave from one of those watch crystals.

There are a bunch of schematics on line for this.

You could go old school and use a CMOS 555 without the crystal or even a single transistor or two transistors (with or without the crystal) as an oscillator just for testing.

Just be careful to keep the signal level reasonably weak and commoned  to and  at or below the supply voltage of the board so you don't cook anything.

i am building one with a 4049. etching the pcb now.

[gkmaia]

Ok, so the results are not good. I got a nice signal out of the original crystal and the new crystal with my built 4049 oscillator. Tested the var cap and it is good. Tested all the other components as well. All traces have continuity the ones that did not are fixed. Still no pulse. 

Just a steady 1.5v at the crystal input and 750mv at it's output. All voltages across the board are either 1.5v or 750mv.

My only conclusion is that either i fried the IC at some stage or the little bit of battery electrolyte was enough to. 

[AlexeiJ1]

Okay so here is my secret stash of circuit boards for these babies:
http://stsupplyonline.com/catalog/8943-citizen-circuit-p-21065.html
Don't mind the 8943 nomenclature. The part number is the same for the 8944 8945 or 8943 models. The difference is the LCD.

I will have a spare board that doesn't have a working buzzer if you wanted it.
Otherwise I would look on ebay for 279-332. It comes up on ebay from time to time. I've bought a replacement for 20$ from the UK recently.

List of parts here:

http://boley.de/en/caliber/watchmovements/citizen/2863

And trust me, your not the only one struggling.

I have 16-17 of these watches in my drawer. I only scavenged 2 working boards from them all. 3 LCD's were working, the rest cracked.

I frequently get them from eBay India for peanuts. Before COVID they were sending free international post, usually 15-25$ AUD for a broken one. Good signs are usually when they come with a flat battery and/or no battery acid.

These boards are super fragile, I have no idea why.

Edited October 8, 2020 by AlexeiJ1

[gkmaia]

This is gold!!!! Thanks mate!! I will have a look for sure!

[gkmaia]

I suspect they were the same boards, but was not sure. Reason being the all had the same features and same LCD labels. That was clever. Nice way to preserve the whole circuit and evolve the case. 

I would be keen to get your PCB with a missing buzzer. I am obsessed with this little fella. 

Where about you are?  I am in NZ.

[gkmaia]

I would say the circuitry in this IC is so simple and so crude that it does not allow for any protection against shorts, etc...

[JohnR725]

1 hour ago, gkmaia said:

I would say the circuitry in this IC is so simple and so crude that it does not allow for any protection against shorts, etc...

just as a reminder this isn't your normal integrated circuit. The watch companies are manufacturing their own components now more than likely was manufactured in house very specific for what it's used for. Sealed up in a metal case they probably didn't expect that they get exposed all sorts a bad undesirable stuff.

Then there is the other little problem what was the life expectancy of this watch? things change considerably when you're designing a circuit to last for a very long time in very harsh environments versus having it sealed up in a metal case run by a watch battery and you only wanted to last for? What would happen if they made watches it lasted forever how many more new watches what they sell. They probably not deliberately designed to fail but they weren't made the last forever either.

then there's another problem the program do they use ROM or did they use programmable memory? Even some of the analog quartz watches use logic programming to regulate the frequency of the crystal they abandoned trimmer capacitors. What is the life of that memory? I did a quick look here's the first link I found notice they're suggesting 10 years?

https://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv021.cgi?read=237068

 

 

[gkmaia]

For sure. I did not say it on a bad way. They had to be cost effective give how amazing these watches were at the time.

[JohnD]

57 minutes ago, JohnR725 said:

just as a reminder this isn't your normal integrated circuit. The watch companies are manufacturing their own components now more than likely was manufactured in house very specific for what it's used for. Sealed up in a metal case they probably didn't expect that they get exposed all sorts a bad undesirable stuff.

Then there is the other little problem what was the life expectancy of this watch? things change considerably when you're designing a circuit to last for a very long time in very harsh environments versus having it sealed up in a metal case run by a watch battery and you only wanted to last for? What would happen if they made watches it lasted forever how many more new watches what they sell. They probably not deliberately designed to fail but they weren't made the last forever either.

then there's another problem the program do they use ROM or did they use programmable memory? Even some of the analog quartz watches use logic programming to regulate the frequency of the crystal they abandoned trimmer capacitors. What is the life of that memory? I did a quick look here's the first link I found notice they're suggesting 10 years?

https://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv021.cgi?read=237068

 

 

Fortunately Seiko didn't take the obsolescence/short life approach with their first true production quartz analogue movement, the 3803...

https://i.imgur.com/S7WZCgX.jpg

Or indeed with their mid 1970's 'work horse' movement, the 0903, which is virtually bomb proof, both electrically and mechanically....

https://i.imgur.com/HhPskYe.jpg

[AndyHull]

The "condensers" are about the only things you can suspect, and have a chance of actually changing. They are pretty important. The "boosting" ones probably generate the split supply for the LCD and possibly other parts of the circuit. They may also be used for a charge pump boost the voltage to drive the rotor.

The chip is CMOS, so it is possible that it may be susceptible to damage by static electricity, but possibly impact and moisture are more likely candidates to kill the silicon.

If you have a working external 32768 Hz  oscillator (exact frequency for testing is probably not critical), and can inject a signal in to Xin (you may need to disconnect the crystal first) you might have some luck.

Actually you might be able to just touch the X in input with one finger and inject a little random noise there the display may flicker in to random life. If so, the chip is probably OK. 

Without a working oscillator, I doubt if you wont see anything on the display, because the boost circuits for the LCD almost certainly rely on it and therefore wont work.

Having a working board to compare with would also be a big help.

Edited October 8, 2020 by AndyHull

[gkmaia]

49 minutes ago, AndyHull said:

 

The "condensers" are about the only things you can suspect, and have a chance of actually changing. They are pretty important. The "boosting" ones probably generate the split supply for the LCD and possibly other parts of the circuit. They may also be used for a charge pump boost the voltage to drive the rotor.

The chip is CMOS, so it is possible that it may be susceptible to damage by static electricity, but possibly impact and moisture are more likely candidates to kill the silicon.

If you have a working external 32768hz  oscillator (exact frequency for testing is probably not critical), and can inject a signal in to Xin (you may need to disconnect the crystal first) you might have some luck.

Actually you might be able to just touch the X in input with one finger and inject a little random noise there the display may flicker in to random life. If so, the chip is probably OK. 

Without a working oscillator, I doubt if you wont see anything on the display, because the boost circuits for the LCD almost certainly rely on it and therefore wont work.

Having a working board to compare with would also be a big help.

Tested the condensers on a LCR meter and they are fine. I have built an oscillator and the original crystals work fine. definitely a problem with the iC. 

[AndyHull]

Just now, gkmaia said:

Tested the condensers on a LCR meter and they are fine. I have built an oscillator and the original crystals work fine. definitely a problem with the iC. 

If you have a hot air rework station, you could hit it with some heat to re-solder it. This assumes it is not wire bonded rather than soldered of course. 

 

[gkmaia]

Yes got a PACE MBT station. But the board is just too delicate to heat it up i am afraid it will bulge and also too close to the crystal. Just did low temp iron, wick and lots of patience. Apart from the IC all the other components are discreet components and they all tested fine. 

With the new boards that will arrive will be great to see it and I will also make some charts of the signals to share.

Had some experiments with glass bead blasting at low PSI. looks really nice.

Edited October 8, 2020 by gkmaia

[AlexeiJ1]

15 hours ago, gkmaia said:

I suspect they were the same boards, but was not sure. Reason being the all had the same features and same LCD labels. That was clever. Nice way to preserve the whole circuit and evolve the case. 

I would be keen to get your PCB with a missing buzzer. I am obsessed with this little fella. 

Where about you are?  I am in NZ.

I'm in Australia.
I'm just waiting on a parcel that has been 6 weeks from US to replace my dodgy board, then I'll message you.

I have a Seiko 7549 bezel that needs glass bead blasting, I'd love that frosted finish - anychance you can help?

[gkmaia]

9 minutes ago, AlexeiJ1 said:

I'm in Australia.
I'm just waiting on a parcel that has been 6 weeks from US to replace my dodgy board, then I'll message you.

I have a Seiko 7549 bezel that needs glass bead blasting, I'd love that frosted finish - anychance you can help?

Sure I can help you, no cost as well. I will send you a private message. Just need to strip it all like I did and glue, dirt and grease should be all removed before otherwise the beads wont impact the metal.

[gkmaia]

Trying to remove deep scratches from the glass. Seems to be working so far... 

[gkmaia]

Sadly I was looking great... flat all scratches removed... was my last pass and when washing it i dropped and it broke... 

spent 2 hours polishing it...

[gkmaia]

Would you know if there is a website like the https://boley.de/ but with codes for the case parts? So I can find the number.

By measuring it seems 27.3mm x 2.1mm.

https://www.esslinger.com/watch-crystal-flat-round-mineral-glass-crystal-2-0-mm-thick/

I am just not a 100% sure I can trust my gauge

Edited October 9, 2020 by gkmaia

[AlexeiJ1]

On 10/9/2020 at 7:51 PM, gkmaia said:

Would you know if there is a website like the https://boley.de/ but with codes for the case parts? So I can find the number.

By measuring it seems 27.3mm x 2.1mm.

https://www.esslinger.com/watch-crystal-flat-round-mineral-glass-crystal-2-0-mm-thick/

I am just not a 100% sure I can trust my gauge

There is a case section on Boley.de.
I just typed in 087836 as the case number.
Check if that is correct:
https://boley.de/en/case-parts/citizen/7099.4-087836?q=087836&p=0&s=50&l=7
The crystal is a 54-L0303H
There is one here: https://www.sapphytimes.com/citizen_crystals.html but you have to email them and check stock.

Ebay don't have any.
I'd just fit a generic flat crystal. I usually order 1 size down, 1 size up, 1 size correct.
Watchmakers usually (break one, fit one, keep one).

I use cousinsUK for crystals. They have more sizes than esslinger. To be honest esslinger dont stock a whole lot of anything compared to cousinsUK.

You can't rely on one place for reference information.
I use Jules Borel, Boley, Cousins, Seiko PDF's (search caliber + pdf), citizen PDF's, forums, etc.
Sometimes CousinsUK will list the part number for a caliber such as 8943 that will then let you track it down even if out of stock. That's how I found my first replacement NOS 8944 circuit board and LCD.