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Where's the CMOS Battery?

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First post, by Gahhhrrrlic

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So I just moved on to a different computer in parallel with my longer term project (386) and so I checked all the hardware, set the non-PNP jumper stuff and powered it up to see what would happen. The BIOS settings were all wrong and I got a warning: "CMOS battery failed"

I've gotten this warning before... actually I got it on my 386 I just finished playing with but I fixed that a while back by yanking the crusty old ni-cd and replacing it with a Li-Ion battery. This board here... I can't find the battery! I looked everywhere and I can't find it. The board in question is a Shuttle HOT-557 board that looks like this:

http://mail.lipsia.de/%7Eenigma/neu/pics/i430VX.jpg

Maybe I'm blind but I don't see a battery anywhere at all. Now what am I going to do? If there's no battery to replace I can't change my BIOS settings 🙁 This is going to present many problems. Could it be that they are using a capacitor instead of a battery?

https://hubpages.com/technology/How-to-Maximi … -Retro-Computer

Reply 1 of 33, by Jed118

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That thing labelled DALLAS - That's where the battery is. You'll have to drill it out and replace it.

First Google search I saw:

https://www.youtube.com/watch?v=NdlSfqto_0o

I've done this three times - Once I got lucky and the chip had a plastic cap on it.

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I still managed to break the leg off the IC, good thing I have 40,000 hours of precise bodywork under my belt and 6/10 soldering skills (on a good day)

Other times, drill baby, drill!

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Sometimes, these SOBs won't let you boot if the RTC is dead.

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Reply 2 of 33, by Gahhhrrrlic

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Oh you gotta be sh*ting me!!! Whoever designed this ought to be shot!

I'm assuming there's a good reason to do this rather than just replace the entire RTC?

https://hubpages.com/technology/How-to-Maximi … -Retro-Computer

Reply 3 of 33, by Jed118

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There's a whole CMOS chip in there. Same DIP package as an IBM PS2 model. Good luck getting the right one 😉 Not sure why this was done, it makes as much sense as having a car's ECU harness facing the front of the car underhood, in line with the hood gap, right where the road salt and water can hit it the best (I'm looking at you, DaimlerChrysler) in such a way as to corrode the contacts.

It's honestly not that hard. I've done one after a few beers and it came out better than the ones pictured here 😁

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Reply 4 of 33, by shamino

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I haven't looked recently but I think the DS12887A has generally been available on eBay. Of course some of them might be old.
If your chip is socketed then replacing it would surely be easier. If it's soldered then it's your call. If you decide to desolder it then at least install a socket, in case the replacement dies soon.

If you're not experienced with desoldering then it's usually safer to cut the pins off near the body of the chip, then you can desolder the pins one at a time. It's easier that way.
EDIT: I guess cutting the pins on a Dallas chip might not be that easy. I forgot how those things have such a bulky body that they cover the pins.
I suppose it *might* be possible to pull on the chip and see if it leaves the pins behind - but if that doesn't work you could cause serious board damage by ripping traces. So that's probably a bad idea.

Reply 5 of 33, by Gahhhrrrlic

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I guess since it's an RTC, it shouldn't be socketed already but the fact that it has a battery changes all that. What were they thinking? Even from the factory, it looks hackish to solder onto a battery like that and cover the whole mess with potting material. Facepalm.

Oh well thanks for all the help. This is most certainly the problem so I will either have to give up or fix this. I think it might be best to uninstall everything and pull the motherboard so I don't destroy it when I remove this chip.

https://hubpages.com/technology/How-to-Maximi … -Retro-Computer

Reply 6 of 33, by sf78

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shamino wrote:

I haven't looked recently but I think the DS12887A has generally been available on eBay. Of course some of them might be old.

I'd say it's 99% sure you will get one with a dead battery. I've bought several from different sellers, all DOA. The whole DIY fix is a very simple job, it will take around 5-10 minutes once you get going. Remember to test the current flow afterwards.

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http://www.classic-computers.org.nz/blog/2009 … attery-chip.htm

Reply 7 of 33, by jamesp15

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Digikey sells new ones, I would think mouser and other big name electronics distributers would as well.

for ~$10 each for a recent stock one from a reputable distributer isnt a bad price IMO. The last 5 that I bought last August were week 50 of 2016 (1650) datecode.
https://www.digikey.com/product-detail/en/max … 2887--ND/956874

If you remove the old one to solder one a new one, i highly reccomend getting one of these for each one you do:
https://www.digikey.com/product-detail/en/3m/ … 5467-ND/1133620
(Just trim off the leads from the socket that are not present on the Dallas chip.)

I usually replace them on older boards that I get a hold of, and keep the old ones that later I modify with a CR2032 holder as a backup.

Reply 10 of 33, by Jed118

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derSammler wrote:
Second that. Did the same on my Intel NX mainboard. […]
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Second that. Did the same on my Intel NX mainboard.

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That's quite neat.

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Reply 11 of 33, by PTherapist

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sf78 wrote:
shamino wrote:

I haven't looked recently but I think the DS12887A has generally been available on eBay. Of course some of them might be old.

I'd say it's 99% sure you will get one with a dead battery. I've bought several from different sellers, all DOA. The whole DIY fix is a very simple job, it will take around 5-10 minutes once you get going. Remember to test the current flow afterwards.

I guess I'm in the lucky 1% category, I ordered one last year from eBay and it's working great in my Socket 5 motherboard. The board wouldn't boot an OS without a working battery. Don't know how much life it has left in it, but I have 2 spares and could do that DIY hack if worst came to worst.

Reply 12 of 33, by Gahhhrrrlic

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Based on what I'm seeing so far, it looks like the easiest way to do this is just remove the MB from the case and dremel it in-place. Probably the most dangerous way to do it but then again it could also be dangerous to try to remove the chip from the board if you don't know how to do it properly like me. I've never desoldered anything with more than 2 legs before and I'm afraid to start on this piece of hardware.

https://hubpages.com/technology/How-to-Maximi … -Retro-Computer

Reply 14 of 33, by derSammler

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These modules were simply cheaper, since it was a single compenent instead of having ~10 parts on the mainboard for the same function. Also, the internal battery lasts for at least 10 years, that's an eternity for a computer mainboard. That people are still using 20+ years old mainboards these days wasn't intended.

Apart from that, if you look at most smart phones and similar devices today, not much has changed. It's obviously intended that a device dies with its battery.

Reply 15 of 33, by Radical Vision

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Yeah the cost but of course, how did i not remember that is NO 1 that matters for all manufacturers to reduce the cost.. Some times they did retarded stuff like this, or using crap capacitors, and that make one piece of hardware more bad then it should be...

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Reply 16 of 33, by Jed118

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Gahhhrrrlic wrote:

Based on what I'm seeing so far, it looks like the easiest way to do this is just remove the MB from the case and dremel it in-place. Probably the most dangerous way to do it but then again it could also be dangerous to try to remove the chip from the board if you don't know how to do it properly like me. I've never desoldered anything with more than 2 legs before and I'm afraid to start on this piece of hardware.

Use a soldering wick or a suction gun. I've done DIPs with these tools and while it does take a while, it eventually gets done.

I'm actually eyeing a 486 board online for $3 with the exact issue you're having. Soldered on Dallas. I think I'm going to take up the challenge 😉

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Reply 17 of 33, by badmojo

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I’ve modded one of these without removing it from the motherboard and it’s was fiddly but possible:

It's 286 time!

I wouldn’t do it again though - as suggested by Jed118 I use wick now for desoldering. Just practice on something else for 15 mins first.

And yes these things are annoying but 100% better than a dead motherboard due to a battery that leaked.

If it's broke, then fix it!

Reply 18 of 33, by Jed118

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badmojo wrote:
I’ve modded one of these without removing it from the motherboard and it’s was fiddly but possible: […]
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I’ve modded one of these without removing it from the motherboard and it’s was fiddly but possible:

It's 286 time!

I wouldn’t do it again though - as suggested by Jed118 I use wick now for desoldering. Just practice on something else for 15 mins first.

And yes these things are annoying but 100% better than a dead motherboard due to a battery that leaked.

That's quite a good repair. The 486 I'm bidding on now has that same problem, but the RTC is facing a resistor pack. I would have done it your way if I could.

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Reply 19 of 33, by badmojo

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Jed118 wrote:

That's quite a good repair. The 486 I'm bidding on now has that same problem, but the RTC is facing a resistor pack. I would have done it your way if I could.

Thanks and yes I got lucky with the placement. It's still kicking with that battery I put in originally.

If it's broke, then fix it!