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National Semiconductor WM-09 help

For electronic related stuff like module repair, silver epoxy fixes etc.
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edgeofsanity

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National Semiconductor WM-09 help

Post26 Aug 2015, 02:24

As mentioned in my intro post, I've recently acquired my first LED vintage watch! I (potentially) really like it, as it's both retro cool, and has clean lines. I've always liked my watches to have clean, simple faces as well, and there's nothing cleaner than an LED watch display. ...especially when it's broken. :-(

So, appearance-wise, I like this watch a lot. Unfortunately, the module seems to need some help. And I'm about as far from an expert on this as is possible. I've spent a lot of time perusing this (and other forums), and I see lots of talk and advice on people repairing their modules via soldering and electric paint pens and whatnot. Certainly I'd be willing to give those things a try if they're relevant in my case, and if it would be worth it. Sending out for repair or replacement is another road I'm willing to go down if it's financially reasonable. I'm just not sure what my best options are here.

You’ll see from the attached pictures that the little metal springy contacts on the + side are gone. And it looks like someone might have taken some sandpaper or something to them at some point to clean them? Also one of the little retainer prongs for the battery hold-down is broken off (was hanging by a thread when I opened the back).

I tried putting new batteries in anyway, and did get some form of life out of it, as a “W” appeared in one of the LEDs. Trying a second time briefly got me an “E” in another LED. Trying a third time gave me a full display for a brief second before it went dark again. That was it though. It wouldn’t show or do anything else after that.

Again, thanks for any help or opinions on this!

20150821_172307 [129216].jpg


20150821_172241 [129214].jpg
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SASM

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Re: National Semiconductor WM-09 help

Post26 Aug 2015, 08:06

National semiconductor modules are usually easy to repair as you have to change the quartz only. Get you a 32khz watch quartz and replace the original component. But be VERY careful, as the soldering pads are located exactly above the chip. Too much heat means you will destroy the wirebonds on the front side and this will destroy your module.

If you are not successful, then I have a replacement module in stock, the SASM55. This module is a perfect 1:1 replacement for all National Semiconductor modules. But go ahead and try to Change the quartz first.

Hanno.
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edgeofsanity

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Re: National Semiconductor WM-09 help

Post26 Aug 2015, 14:52

Ok. Thanks for the reply SASM!

A couple follow-up questions if you don't mind:

What would you recommend I do about the missing springy contacts for the + battery connection? As it is right now, the battery on that side sits much lower and looser in its slot. Sort of gives me the impression contact is iffy. Would a couple dots of solder do the trick?

Also, is there a specific type of soldering iron and solder preferences for this type of delicate work? I assume an electric iron is preferred? I ask because to date the only soldering work I've done is on the wiring of my old pickup truck and car. I use a mini butane torch with soldering tip for that. Good enough for the 14 and 16 gage wires in question in those instances; but seems like it might be overkill for delicate circuit board work.

Also, if you could PM me a general price quote for the SASM55... so I can know what I'm dealing with as far as weighing the cost options of this project.

Thanks again!
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Re: National Semiconductor WM-09 help

Post28 Aug 2015, 15:24

Ok, small update.

I remembered that my old electric wood burning kit came with a soldering tip, so I used that last night to try and build a better + side contact. It worked! Sort of.

It wasn't exactly pretty but I managed to lay down a gob of solder where the + contacts used to be, and I got a fully functioning display for about 20 minutes! Obviously the time was wrong, and I had no idea how to adjust it (the lower button -flush with the case- didn't seem to do anything); but it kept good time for those few minutes before it went dark again. Further experimenting with the solder couldn't revive it.

I haven't yet gotten a new quartz. I'm going to see if I can find them locally this weekend. So far though, I'm inclined to think it's a contact battery circuit/contact problem. I know I'm not the expert on these, so if you say I need a new quartz I'll give it a shot; but having that full display last night really threw me.
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Re: National Semiconductor WM-09 help

Post28 Aug 2015, 22:10

Looks like it could do with a bit of a clean, all that green gunk is an indicator that the traces on the PCB are not going to be very clean, a fibre tipped pen is ideal for this job and they are only a couple of quid on eBay, adding the solder might just have made a better temporary contact, I would remove the plastic holder and clean the traces before doing anything else especially if you have had a 3 or 4 digit display - a faulty QC is usually indicated by a single digit display so with a clean up and a bit of luck you might just get it going again - the setting button is the one that is recessed located at the 4 o'clock position.

Good Luck!

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