is the 1287 and the 12887 compatible?

Ze_ro wrote:

So the clock battery on my Pentium 133 machine finally died on me the other day. Strangely, this has left the computer completely unusable! When I boot, it forces me into the CMOS to restore settings, but upon leaving the CMOS setup, the computer immediately reboots and forgets everything I just entered! Great work there, QDI (whoever they were...)

Oh well, I would have replaced the battery regardless, but to my horror when I opened the case, I found that the battery was not in a simple coin holder, nor even soldered to the motherboard... instead it is embedded into the substrate of the clock chip! I looked on the net for some information, and I found instructions on how to grind away the chip casing to expose two of the pins to solder a new coin-cell holder to replace the embedded battery. Has anyone here done this and maybe can provide some insight on the process?

Yeah… this should be in Wikipedia as an illustration for a term "hack job". Don't do this. The right way to go is desoldering the old 'chip' (if it's not socketed already), soldering in a socket and installing replacement chip. Batteries in these chips last long, replacement parts are easly available and doesn't cost much. Another less elegant and more costly solution (but still waaaay better than drilling holes) would be https://www.ebay.com/itm/GW-12887-1-DS12887-R … e-/273322727960

Yrouel wrote:

Someone also made a replacement assembling the parts on a pcb http://www.8bity.cz/2014/bateriova-nahrada-rt … ds12887-mk48t87 (in polish but you can see the pictures)

That's Czech not Polish (if you can't identify the language, then at least take look at the top level domain - .cz like CZech, .pl like PoLish 😉

arncht wrote:

is the 1287 and the 12887 compatible?

Yeah, direct replacements. AFAIK one has y2k bug, the other doesn't.

Thanks for all the tips. I have a Asus P.Pro board with soldered DS12B887 that needs a new battery and do not want to unsolder the old timer if at all possible. Going to try the add-on ext.battery method first.

Ze_ro wrote:

When I boot, it forces me into the CMOS to restore settings, but upon leaving the CMOS setup, the computer immediately reboots and forgets everything I just entered! Great work there, QDI (whoever they were...)

That's not the fault of QDI. There's the common misunderstanding that people think the CMOS is powered by the system once it's turned on. But that's not the case. The Dallas chip has no pin for external power, it can only ever be powered by the battery inside. So with an empty battery, you have no working CMOS. The CMOS however is crucial and the system (or rather the BIOS) can not work without it.

I don't understand the reticence to do this very basic job, it's actually very easy do in-place, MUCH easier than unsoldering/fixing/resoldering. The only qualification is, you need to have clear access to the side of the case opposite pin 1 for the Dremel bit. See details in this post:
Replace Dallas RTC battery without desoldering?

precaud wrote:

I don't understand the reticence to do this very basic job, it's actually very easy do in-place, MUCH easier than unsoldering/fixing/resoldering. The only qualification is, you need to have clear access to the side of the case opposite pin 1 for the Dremel bit. See details in this post:
Replace Dallas RTC battery without desoldering?

Because some times the Dallas clock chips are not that accessible. In the long run it may be quicker/better to remove the chip and place a socket it place. Another thing some people just don't have the skill set and/or equipment to carry out the task.

Jo22 wrote:

I bet you haven't seen old 68k Macintoshes, yet. Without a battery they appear to be completely dead. ;-) […]
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Ze_ro wrote:

So the clock battery on my Pentium 133 machine finally died on me the other day. Strangely, this has left the computer completely unusable! When I boot, it forces me into the CMOS to restore settings, but upon leaving the CMOS setup, the computer immediately reboots and forgets everything I just entered! Great work there, QDI (whoever they were...)

I bet you haven't seen old 68k Macintoshes, yet. Without a battery they appear to be completely dead. 😉

Half-Saint wrote:

I know this is an old thread but it's not ancient so I'll just leave this here. […]
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I know this is an old thread but it's not ancient so I'll just leave this here.

I just spend a couple of hours destroying 4 out of 5 dallas 1287 and 12887 chips that I got from the chinese. It looks like all of them are pulls rather than old stock. Some of them had really weird values stored which made my old motherboard go bonkers.

So I took a hammer and a chisel to all four of them, destroying them in the process. I was trying to see, if I'd be able to free the chip itself from the silicone. In two cases I succedded but not without destroying both crucial pins for connecting the new battery. The chip inside is DS1185 but looks like it's impossible to buy on eBay or Aliexpress or Farnell for that matter.

Anyway, I'm down to one last chip from this batch and I don't want to waste it so I'll try to dremel this one with a cylindrical grinder bit. I tried this twice before but it didn't work the first time as it appears I grinded the chip leg and 2nd time I lost patience ad hammered it 😁

Don't worry, fixing old Dallas clocks isn't that difficult. Just requires time, patience and a bit of sleight. 😉
When you get used to it, it is even fun. You know, the same kind of fun like jumping in icy water or standing upon thorns.
The first time was a bit stressing for me, too.

Here's a tip: If you have got an old soldering iron, you can melt your way through to the coin cell (if it is a plactic case).

But please don't use a quality soldering station for this (don't use a good ol' Weller for this!)
Another method is using a file. It takes time, but your'e less likely to damage anything.
Tried both methods myself.

Either way, the internal battery doesn't have to be removed. If you cut connection to one pin, it won't cause damage anymore.
And forget about the acid. Coin cells do carry very little of it. And after about +20 years, that liquid might be even seared.
If your're still worried about this, though, just use a tiny bit of hot glue (drown it in hot glue!).

Anyway, good luck! 😀

my Power Mac 6100 requires turning it off and back on for it to power on without a PRAM battery but my Performa 630CD still powers on regardless having a battery or not, i noticed that the Performa 630CD keeps the date and time when it's still hooked up but it loses it when i unplug it, but the Power Mac 6100 loses the settings as soon as i power it off, i guess because the Performa has standby power and the Power Mac is either off or on.

Caluser2000 wrote:

Because some times the Dallas clock chips are not that accessible. In the long run it may be quicker/better to remove the chip and place a socket it place. Another thing some people just don't have the skill set and/or equipment to carry out the task.

I agree ! Have done a few that were socketed but none soldered yet. Is why I read thru this thread a few times as the next board I do is soldered am afraid of ruining it. Here is my last fix, a socketed on Giga GA486IM 486 (but if soldered would be near impossible to fix without unsoldering).
Found that the micro metal side grinder for Dremel works best, less vibration during cutting (which could and has damaged the Xtal inside on a few other attempts)

Desoldering is a pain without the proper tools.
I simply cut off one side of the pins with a box cutter, break off the chip, desolder the remaining pins one by one and solder in a socket. It only works with easily accessible chips. I usually just stay away from boards with integrated batteries because there are a lot of better alternatives.

Recently reworked my first DS1287, it was a breeze. I expected it to be much harder, but using a hacksaw blade I uncovered the battery pins in no time. After seeing the first tiny bit of metal I used the tip of a box cutter blade to scrape the resin, especially at the negative pin, and cut the link to the internal battery with said cutter blade. Attached the CR2032 holder on top with strong double adhesive tape, made the connections and good to go.
Since embarking in the retro craze some two years ago I've pretty much avoided motherboards with Dallas modules, but these days I'm beginning to see them as a blessing, after coming across countless oldies destroyed by the NiCad barrels.

quicknick wrote:

Since embarking in the retro craze some two years ago I've pretty much avoided motherboards with Dallas modules, but these days I'm beginning to see them as a blessing, after coming across countless oldies destroyed by the NiCad barrels.

Yep I'd much rather desolder a 24pin DIP and put in a socket than deal with VARTA cancer being spewed all over hell and rotting traces and vias.

Caluser2000 wrote:

Because some times the Dallas clock chips are not that accessible. In the long run it may be quicker/better to remove the chip and place a socket it place. Another thing some people just don't have the skill set and/or equipment to carry out the task.

That's why I qualified it IF the pins on the side opposite Pin1 are accessible. Probably an inch of clearance is plenty. But not all will have that.

I bet more people have a Dremel, and know how to use it, than have a desoldering rig. I have two industrial-grade vacuum desoldering systems and this is a far preferable solution. The desoldering route is neither quicker nor better.

You can definitely make the argument that carving up the original package is faster, but I object that it is better.

I don't really care what "most people" own. That has no bearing on what is the objective best way to solve a problem. My position is that having a brand new sealed unit in a socket is superior to a carved up mess with wires sticking out.

You can buy button cell replacements RTCs packs to fit in those sockets from the likes of MonoTech PCsor Glitchworks. https://monotech.fwscart.com/DS12887_RTC_Drop … 4_19810725.aspx

maxtherabbit wrote:

I don't really care what "most people" own. That has no bearing on what is the objective best way to solve a problem.

That's an irrational argument. This is a public forum, and suggestions that apply to "most people" are by definition more relevant.

And it does have a bearing. If someone doesn't have access to a tool (desoldering), then that approach is off the table, superior or not.

And if you've ever done any desoldering work, you would know that it is not a 100% good outcome. Traces can be damaged by it. This is particularly a concern with multi-layer circuit boards, which all computer boards are.

My position is that having a brand new sealed unit in a socket is superior to a carved up mess with wires sticking out.

Aesthecally, perhaps. But functionally, I disagree. Adding a battery holder to the chip in situ is the high-percentage-outcome, least harmful approach.

FYI, theres also ds12885, that is only the chip. No need for drilling or anything. 😉

precaud wrote:

And if you've ever done any desoldering work, you would know that it is not a 100% good outcome. Traces can be damaged by it. This is particularly a concern with multi-layer circuit boards, which all computer boards are.

I have to agree, desoldering is a pain if you only have basic tools. Varnished boards are much harder to solder. Desoldering braid isn't a magical tool either that just removes all traces of solder after 5 seconds. Soldering for too long also causes the solder joints to peel off. It's super easy to ruin a multi-layer board with prolonged soldering. It's not worth it.

I have the tools and ability to desolder DIPs from multilayer boards without a meaningful chance of damage. If you don't, perhaps consider git gud

It's not the aesthetics of grafting a battery on to the thing that bother me, it's the mechanical fragility.

maxtherabbit wrote:

I have the tools and ability to desolder DIPs from multilayer boards without a meaningful chance of damage. If you don't, perhaps consider git gud

It's not the aesthetics of grafting a battery on to the thing that bother me, it's the mechanical fragility.

Or just do it our way.

There are tons of applications for a good desoldering station and a set of skilled hands to operate it. I would recommend getting squared away with one to any retro enthusiast, dallas clock battery or not.