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Compaq SLT 386's 20

Compaq SLT 386 and DS1287 clock battery

Compaq SLT 386 and DS1287 clock battery

Frozenfire,

You're in luck! (Sort of). I also have a Compaq SLT 386 "laptop" (the kind with the handle), and I actually just fixed the clock battery problem. Be forewarned, it is a little involved, however. These models use a Dallas DS1287 real time clock, battery, and crystal combination 20-pin DIP. This means that you can't just open it up and pop in a new coin battery. What you can do, however, is actually cut into the chip, and solder a new battery into it. I know it sounds crazy, but there are detailed instructions available here:

http://www.mcamafia.de/mcapage0/dsrework.htm

I followed them and didn't have any issues; used a Dremel to cut into the chip at pins 16 and 20, and soldered two wires, which I then ran out into the battery compartment, and then soldered a Radio Shack 2xAA battery back. You could also try a coin-holder and CR2032, if you wanted.

PS; if you do this and succeed, let Peter at mcamafia know, he will appreciate it. Also, the battery is kind of important; seems to be more than just the clock at issue. I wasn't able to boot from the hard drive until I fixed the battery, I guess the BIOS needs to know the hard drive type in advance or something.

Speaking of BIOS, you will need the Compaq "Diagnostics Disk" to access it. I found it here:

http://members.driverguide.com/driver/detail.php?driverid=73221

I had to extract it onto a 720K DD floppy, but you might be able to convert the image to a 1.44 MB floppy or something.

Best of luck, and let me know how it works out! The SLT 386 is a great laptop, very sturdy, and easy to disassemble. Another option would be to buy a new Dallas chip and replace the dead one, but I think it would be difficult to get the old one out, and it's hard to find truly new ones (and they may be a little pricey).

Gabe

I attached a few pictures from when I did this project...
 

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Well done on tackling the issue and suceeding Gabe. I have the same problem in my Compaq SLT/286. I read those instructions on how to cut open the chip and add a piggy-back battery some time ago and it scared the hell out of me :)

The machine boots just fine, so I just live with the error codes.


Tez
 
Thanks for time you spent to type that up, however I posted that a long time ago around the 1st of nov. the system is long gone now, I got tired of waiting and toke it upon of myself to try to open and find the battery, after not finding out how to open it, (I don't do work on laptop's at all and this is one more resaon why I don't) I ended up prying it open with a hammer and flathead screw driver got the metal cage out that's just as bad to get in to, So I said screw it, if thay can't make it easy and ect to work on remove parts, I don't want it! Who want's do go thought that to change a dammn battery then on top of that cut the chip up and do all the crap!
 
You can get cheap torx screwdrivers/bits from harborfreight or whatever that tool place is called ($10 a set is what I paid for a set that I needed to work on my mac wallstreets).

The problem with mail order places that sell Dallas chips is they screw you on shipping or have a minimum purchase or $20 or more.
 
The problem with mail order places that sell Dallas chips is they screw you on shipping or have a minimum purchase or $20 or more.

Yes, I found opening the case no problem once I had the right screwdrivers. The shipping costs to NZ though, is one of the reasons I'm just gonna live with the problem.

Tez
 
Well done on tackling the issue and suceeding Gabe. I have the same problem in my Compaq SLT/286. I read those instructions on how to cut open the chip and add a piggy-back battery some time ago and it scared the hell out of me :)

The machine boots just fine, so I just live with the error codes.


Tez

I successfully did this fix on my SLT/286 some months back. It works just fine, and the hack can be done with a sharp knife instead of a dremel, so that you can cut away little by little of the plastic.

I could not boot from the HDD unless I had the chip fixed, so that's why I did it.
 
Well done on that. It looks like an intricate procedure.

I'd probably try it if mine couldn't boot. After all, if the thing doesn't work anyway, you have nothing to lose, right?

Mine does recognise the HD ok, although I might pluck up the courage to try modifying the battery chip one day. The machine doesn't recognise the floppy drive and I'm sure that's because the CMOS setting defaults to a 720k drive rather than the 1.44 that's installed. In the meantime I just use MS-DOS 5.0 INTERSRV to get files into the machine.

Tez

I successfully did this fix on my SLT/286 some months back. It works just fine, and the hack can be done with a sharp knife instead of a dremel, so that you can cut away little by little of the plastic.

I could not boot from the HDD unless I had the chip fixed, so that's why I did it.
 
I can't see going to all that trouble when you can get DS12887s for about 6 bucks each and just pop them in.

They've worked in every single IBM, Commodore and a few 486 mobos that I've put them in.
 
I can't see going to all that trouble when you can get DS12887s for about 6 bucks each and just pop them in.

They've worked in every single IBM, Commodore and a few 486 mobos that I've put them in.

Yes, but then I would need to order them, and wait 1 week for them to arrive etc etc. The chip-hack is an instant fix, and brings the PC back to life after 30 minutes of work :)
 
I can't see going to all that trouble when you can get DS12887s for about 6 bucks each and just pop them in.

They've worked in every single IBM, Commodore and a few 486 mobos that I've put them in.

Really? I didn't realise you could buy compatible ICs for it. That's good to know.

Still, with shipping costs the way they are $6 becomes $26 and a 2-6 week wait. Add that to our weak currency vrs the US dollar, I might just put up with the problem in the meantime. :)

Tez
 
Ds12887

Ds12887

Really? I didn't realise you could buy compatible ICs for it. That's good to know.
Whilst the DS12887 has been confirmed as a suitable replacement for the DS1287 in the Compaq SLT/286, be aware that in some computers, the DS12887 is not a suitable replacement for the DS1287.

For example, Maxim (Maxim purchased Dallas Seminconductor in 2001) state at: http://www.maxim-ic.com/appnotes.cfm/appnote_number/503
"The DS1287 is obsolete. In many cases, a DS12887 will replace it. However, on some systems, the BIOS or chip set will access the wrong address partition in the DS12887. In those cases, the system will not work."

An earlier thread 'explores' the issue of DS1287 replacement: http://www.vintage-computer.com/vcfo...ghlight=Ds1287
 
Yes, but then I would need to order them, and wait 1 week for them to arrive etc etc. The chip-hack is an instant fix, and brings the PC back to life after 30 minutes of work :)
---------
And it now has a replaceable battery; I've done a couple and yeah, you can finish it in the time it'd take to order a replacement.

m
 
Does anyone know where to find the cable between power supply and computer? Mine is lost. Or if you could just let me know what sort of connector you think it uses ... looks a little like RJ45 both ends.
 
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