Arnex Led Watch Problem

[mervin_fer]

Hi,
I am new to this forum and I need some help.
I just received my Arnex led watch from ebay today and put 2 new SR44 batteries in it and it fired up. Works like a charm. After a few minutes I pressed the button it appears that the digit start flickering and only one digit lights up. I remember reading somewhere, probably in this forum saying that he had put his watch to his car radiator then it work again. I tried heating the qc with my soldering iron and it work for a few minutes.
Question?
Will changing the qc or the trimmer or both solve the problem or is it the ic problem?
Any suggestion would be much appreciated.
Thanks.

[Led-Time]

Hello there and welcome to the forum...

It does sound like the quartz is on it's way out with it working for a bit then showing the tell tale single digit, do you know what kind of module is inside your watch or please post a picture if you can and I'am sure someone be along to help out.

[mervin_fer]

Hi Klippie,
Thanks for the quick reply.
I don't know what module so I'm putting up the pictures you requested.
If you look at the pics, the is no way I can unsolder the qc otherwise I would have already tried replacing it. Thats why I need to confirm this, so I can use a dremel to slowly cut open the qc to excess the leads for soldering the new one.



Thanks again.

[charger105]

Hi mervin.
This is a Hughes module. There are plenty of threads on this forum regarding this module and QC replacement. Do a search and I'm sure you'll find some useful info.
Note that it's not a 32k crystal. You'll have to find an old Hughes QC to replace it with (if that's what you want to do after readng all the threads).
Cutting the QC open with a dremel tool............not a bad idea !

Rgds,
Andrew.

[Led-Time]

In the negative battery well the little brass connector must make good contact with the side of the battery for the quartz to run properly it may just need bent in a little but be careful it's quite brittle and breaks easily, as funny as this may sound one of the main problems I've found with these Hughes modules is the battery contact pads, the material they are made from oxidises with age and this oxide is non conductive cleaning the pads and contacts with a glass fibre pen to a shiny surface again can get seemingly dead modules back to life very quickly, and yours look like they need cleaned.

Sorry to step on chargers toes but I wouldn't put a Dremel any where near a module the vibrations could quite easily damage the fine wire bonds inside.

Hope this helps...

[charger105]

You're not stepping on my toes Klippie. Good point----in hindsight a dremel is a bit brutal.
Ed has mentioned he pulls them out from above, and pokes silver epoxy into the vias to ensure connectivity, with good success. I've never done this, but I did try de-soldering them after removing the lid, with zero success ! It was a few years ago, and I lost my nerve after realising how close the wire bonds were.

Rgds.

[retroleds]

My $0.02
Don't use a Dremel on it - very flawed idea, from both a vibration standpoint, the fact you STILL won't know it is making connection below,limited room and attachment material inside, and unavailability of those crystals(I and others have them, we harvest them off modules that keep good time but have display/logic issues).

The little contact in the negative down battery well. Pull off the plastic battery retainer ring and file the plastic where it comes up to the little bent "ear" of that battery clip - just a few mm. then put the plastic ring back on and bend that ear up a just a little more(the plastic ring will support it against breaking off the board). If a battery pushed in doesn't fall out when turned over, you have it just right.

The quartz crystal will come off the board easily .
With the plastic ring off(of course).
Hold your non-dominant hand palm up, hold module around edges firmly(no pressure on front plastic, there ARE wire-bonds below it), place your thumb between the two battery contacts to further spread the force out, push the top of the crystal toward edge of board(like you are tipping over a tombstone or a drunk...sorry, only visual that came to mind, teenage hi-jinks ). Stuffing a little silver epoxy in the holes is fairly easy, you just pull the epoxy to a nice fine tip by dipping a thin needle in it, cram into the holes in the board. Don't blob any at all outside the hole. If it gets messy, stop and clean the entire area very well with a little isopropyl alcohol on a cotton swab. A few errant grains of the silver could drive you crazy with the symptoms. When you have them crammed fairly full, stick the quartz crystal in and let sit for a few hours. If successfyul, place a small dot of regular epoxy at the base to secure the crystal to the board better. It's not rocket science, just takes a little technique.

Last thoughts: Take a little Lime-Away(or similar product for removing lime and rust stains from toilets and sinks and using a cotton swab, clean the entire boards surface and that plstic ring of any stains from batteries leaked in the past....those disolved metals can cause weirdness. The aluminum battery contacts can be saved from oxidizing by using a little electrical contact cleaner/protector on a cotton swab.

[mervin_fer]

Hi Guys,
Thanks for all the info.
Well I tried bending the contact in the negative well, clean both the battery contacts with contact cleaner still no go. I really want to get this one going guys, as you see in the pic below the case in almost mint condition.

[funkyguy]

silver epoxy.

full step by step guide there ed.excellent.
may i ask what brand / product of "silver epoxy" would you reccomend?
sorry if this info has already been given.

cheers
FG

[retroleds]

may i ask what brand / product of "silver epoxy" would you reccomend?
sorry if this info has already been given.

cheers
FG

I'm using MG Chemicals from Mouser.com...I prefer brands that come in a fairly thin tube, easier to control and they don't seem to have settling/clogging problems in the applicator's tube. Theirs are about the same diameter as a AAA battery. I've bought other that were in squat applicators maybe twice that and they were nothing but trouble....had to resort to squeezing them out into two small jars just so I could use the shit! After cutting the tips completely off.

[Led-Time]

Marvin,

A quick test is to bridge the batteries to make contact and gently wiggle the quartz and at the same time look at the display if it flashes on showing all the digits lit then quickly goes off it's working correctly then it's a quartz connection problem do what Ed said with the epoxy and it'll be fine, if it flickers or shows a single digit then a replacement quartz is needed.

Is there any sign of corrosion around the little trimmer it looks like blue/green crust as this can also give the same fault as a dying crystal the only way to know for sure is to replace it with a known working one.

I see it's a dot type display (no colon) these look the best it would be good to get it going again.

[mervin_fer]

Hi Klippie,
Thanks again and I think you are probably right about the contact problems.I did shake on the qc and adjust the trimmer a little before and I would get it running for a few hours. Yesterday evening I was thinking of joining some fine wires to all the connections but then I taught again. Instead I just soldered the trimmer contacts and added some lead thinking it would probably be dry joints after some 30 to 40 years. After all that it appears to be working more that 24hrs now at the time of this post. Since it's already working so long is it safe to say that the qc is fine even if I get the same problem probably in the next few days. Well all I have to say for now is that I'll keep my fingers cross and hope it works fine. Kippie if this watch works fine you won't see the last of me. See I also purchase a sunwatch kit from Barry and yes it's the mark III and IV parts and I guess I will be needing alot of help from you guys to get it working. It is expected to reach me in about 2 weeks. Any advise before I start? Please let me know. Real good forum to be in. I love you guys. Thanks again.