I am sure that whatever J10 does, it is not a header for external battery. The Dallas DS12877 does not have pin connections for an external battery.

https://ardent-tool.com/misc/Dallas_Rework.html

have a look here, this site might give you pointers on how to dreme .. uhh deal with them pesky Dallas RTCs...

Just uhh forget I mentioned Dremel ok.

You could try one of these, when they come back in stock: https://silvestron.com/store/sb1287-rtc-replacement/

I second the recommendation in the coin replacement chip. So easy! I'll look at your motherboard again for headers. Brand/name of mobo?

I've been happy with this replacement solution:
https://www.tindie.com/products/glitchwrks/gw … acement-module/

Intel486dx33 wrote on 2022-02-22, 21:06:

Hey Guys, I have another NOS 486 motherboard with a Dead Dallas. It does not have connection pins for an external battery but th […]
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Hey Guys,
I have another NOS 486 motherboard with a Dead Dallas.
It does not have connection pins for an external battery but the markings are there for a jumper and traces for an external
Battery connection. PLEASE SEE PHOTOS.

I was wondering if I could add an external battery by soldering onto the motherboard and wires for an external battery ?
And soldering on a wire for the jumper ?

It's possible that those are for a version of the RTC with a clear function (12887A maybe?). I guess that R2 pulls pin 1 of J10 high and that fitting a jumper will connect pin 1 to Ground, which if pin 1 goes to pin 21 of the RTC would clear the CMOS. I don't think any of the Dallas chips have any pins for an external battery, hence the various mods involving cutting in to the casing to get at the internal battery points.

You can check if I've guessed right by measuring the resistance from J10 pin 1 to the Dallas pin 21. If they're connected then it's CMOS clear. If they're not connected then it might be interesting to find out what J10 does connect to.

There are some averagely smarter board designers. This option is rare as it needs footprint to solder battery holder in.

snufkin wrote on 2022-02-23, 10:06:

don't think any of the Dallas chips have any pins for an external battery, hence the various mods involving cutting in to the casing to get at the internal battery points.

DS1385/DS1387 does. But it is far less common that DS12887 or like models.

The problem I have with cutting into the Dallas is that it is right next to the Bios chip so it is impossible to cut into the side of it
Unless I has some sort of small dremil bit which I don’t

I think I will have to desolder the Dallas and use one of those coin battery adapter replacements.
Once I find the right adapter for my Dallas 1287

It might be easier to just replace it with https://www.tindie.com/products/glitchwrks/gw … acement-module/

debs3759 wrote on 2022-02-23, 12:24:

It might be easier to just replace it with https://www.tindie.com/products/glitchwrks/gw … acement-module/

Yes, is that the right one for the DS1287 replacement ?

Yes