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Fixing a Dallas DS1287 Real Time Chip

I tried that once and buggered it up, so I found a replacement on ebay. Seems like I have a few systems with those RTC Dallas chips, one in a PS/2 65 tower and a few in 486 EISA motherboards.
 
Cool project, and great pics. I did that myself not too long ago, but really butchered the RTC as it was soldered to the board and I wanted to make sure the old battery was out and could never be a problem. Added on the same disc style battery and holder as you used

-Lance
 
Cool project, and great pics. I did that myself not too long ago, but really butchered the RTC as it was soldered to the board and I wanted to make sure the old battery was out and could never be a problem. Added on the same disc style battery and holder as you used

-Lance

I guess the main thing is you got it working. Who sees it with the top of the case on anyway :)
 
Tez,
Nice going! As they say, "gutsy is as gutsy does".
-Dave

Thanks. I did have two RTC chips, so it wasn't as big a risk as it could have been. I think if it had been my only one, I might still be thinking about it. :)

Unknown_K, what went wrong with yours? I found the biggest hassel was the soldering as the -ve pin exposed in the chip didn't have much surface area to get solder onto. I used one of those alligator clip and rod "part holder" devices to hold both the wire/battery holder and the IC while I applied the solder. That helped.

Tez
 
For the record, I've done the same mod 4 times with success every time.

Also for the record, Houston Tech modules (another popular one, but very different) are actually much easier because the plastic lid pops right off with the battery exposed underneath. Information surrounding modding the HT modules is really lacking so I try to mention that tidbit anywhere that Google will find it for people who want to know. Basically, the top will just pop off if you try to pull on it (in my case, when attempting to pull it out of the socket on the motherboard, the lid just fell off).

ODIN modules can be modified 100% identically to the Dallas ones as they are 100% compatible drop-ins (model dependent, that is).
 
I'll add that many early (286/386) motherboards were actually engineered to use the MC146818 (they often have headers for external battery supplies) and the DS1287 was just popped in as a shortcut.

In those cases, I recommend going back to the Motorola chip and using the external battery, which can be placed outside of the case. If you're looking toward long-term preservation, batteries have no business being in the same space as a PC board.
 
Yea, you are better off using something removable on older system boards if you can. I try to install a low profile coin type holder in the space the leaky batter was in.
 
Any thoughts about designing a replacement?

Any thoughts about designing a replacement?

Wondering if someone has thought of designing a drop-in replacement for this class of RTC chip.....similarly to the XT-IDE project?

Not everyone has the courage and skills to attempt such drastic surgery (or the spare in case the first attempt fails).

Also, some similar looking RTC chips were available (a long time ago) as drop-in add-on for PCs and XTs - as long as there was an empty ROM socket to put them in.

Maybe the same design could be used for both applications?
 
Wondering if someone has thought of designing a drop-in replacement for this class of RTC chip.....similarly to the XT-IDE project?

Not everyone has the courage and skills to attempt such drastic surgery (or the spare in case the first attempt fails).

Also, some similar looking RTC chips were available (a long time ago) as drop-in add-on for PCs and XTs - as long as there was an empty ROM socket to put them in.

Maybe the same design could be used for both applications?

While I certainly appreciate 'not wanting to mess it up', it truly is quite easy...though there was some blood involved, I did the first one with a pocket knife/saw in my hands...worked flawlessly. If I did it so ridiculously badly and it still worked out in the end I can't see anyone messing it up unless they used C4 to blow the thing to bits.

I forget if it's been listed here, but Peter Wendt's original documentation is here:
http://www.mcamafia.de/mcapage0/dsrework.htm

I believe some brief compatibility info is there as well. In short, not all of the RTC modules are the same - some are so different they'll damage the motherboard or be damaged themselves, even with pinouts attempted to be corrected - there is no generic, fix-all solution for all varieties but it would certainly be doable for each specific model.

For example, if you wanted to make the solution for DS1287s and DS12887s (and I think also the -A version but note it isn't interchangeable in all systems), that could be arranged I'm sure.

Alternatively we could arrange a mail-in system where a few willing members offer to make the appropriate mods to your existing RTC module(s). That takes time and more money than it's worth, though.
 
They'd probably still work, but I question the wisdom of taking something like this on. I think the production volume would be pretty small. Somewhere there's a data sheet from Maxim comparing the 128x and the 168x chips. One thing that jumped out at me was that the 168x chips don't support Motorola bus timings (pin 1, MOT), but then PCs didn't use it.

You can still get NOS MC146818s...
 
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