What's wrong with soldering a new, original Dalls every ~10 years? They're lithium batteries.. no corrosion...and the board/PC has more originality value.

I really hope it doesn't come down to carving up the old 1287 and soldering on a battery

... I also had a lot of trouble with replacement modules. Sometimes they do not work, sometimes the pins for the Dip socket are too thin...
On the other hand the original Dallas Mod always worked without any trouble (it can look a bit ugly though)

JensBV9 wrote on 2024-02-08, 22:58:

Fellow enthusiasts, […]
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Fellow enthusiasts,

First post, but a long time lurker and admirer of this forum.

I recently acquired a Compaq 386N in a really nice condition. It was previously used as a controller for some sort of robotics programming at a university and tucked away for the past 25 or so years.

The Dallas 1287 RTC is obviously way past its prime and in need of some TLC.

Here's what I have:

* With the 1287 present on the motherboard I can boot up with the Compaq Diagnostics Disk and get inside the BIOS for some setup. The settings won't stick, of course, and at reboot the same issues pop up again. Fair enough.

* With an empty socket (1287 removed) the system fails to post and throws a 102-System Board Failure, which is to be expected I guess.

* I ordered and received a replacement RTC module: The NW12887 from Necroware. It has the exact pin layout as the original Dallas DS1287 and I figured it would be as simple as plug and play. However, when I insert the replacement module and turn on the Deskpro I get... absolutely nothing. Just a black screen. The power supply spins up, but that's about it. The onboard VGA-port won't even produce a signal for the VGA-monitor. The disk drive, which works when the original Dallas 1287 is fitted in the slot, makes no attempts to spin up or search for the floppy at all. The computer is pretty much dead, except for the power supply softly humming.

I'm at a loss for reasonably solid leads to investigate further. I really hope it doesn't come down to carving up the old 1287 and soldering on a battery.

So, a couple of questions to round this up:

1. Am I wrong to assume that the Necroware 12887 can replace my old Dallas 1287 in the Compaq Deskpro 386N?
2. Did I somehow manage to order the wrong module?
3. Could the Necroware module be faulty?
4. Have anyone experienced anything like this with a Necroware 12887 replacement?
5. How would you go about trying to fix this issue?

I was saddened quite a bit when I realized I got stuck right away, when I pretty much thought I would at least have a decent shot at booting up the hard disk drive.

All input highly valued and appreciated!

Thanks in advance,
Jens

Does seem that cross-compatibility with the different model RTCs isn't always 100% - probably more a board / BIOS issue than the part itself.

Take it this is your board (version with integrated VGA)...

PC Hoarder Patrol wrote on 2024-02-09, 11:14:

Does seem that cross-compatibility with the different model RTCs isn't always 100% - probably more a board / BIOS issue than th […]
Show full quote

JensBV9 wrote on 2024-02-08, 22:58:

Fellow enthusiasts, […]
Show full quote

Fellow enthusiasts,

First post, but a long time lurker and admirer of this forum.

I recently acquired a Compaq 386N in a really nice condition. It was previously used as a controller for some sort of robotics programming at a university and tucked away for the past 25 or so years.

The Dallas 1287 RTC is obviously way past its prime and in need of some TLC.

Here's what I have:

* With the 1287 present on the motherboard I can boot up with the Compaq Diagnostics Disk and get inside the BIOS for some setup. The settings won't stick, of course, and at reboot the same issues pop up again. Fair enough.

* With an empty socket (1287 removed) the system fails to post and throws a 102-System Board Failure, which is to be expected I guess.

* I ordered and received a replacement RTC module: The NW12887 from Necroware. It has the exact pin layout as the original Dallas DS1287 and I figured it would be as simple as plug and play. However, when I insert the replacement module and turn on the Deskpro I get... absolutely nothing. Just a black screen. The power supply spins up, but that's about it. The onboard VGA-port won't even produce a signal for the VGA-monitor. The disk drive, which works when the original Dallas 1287 is fitted in the slot, makes no attempts to spin up or search for the floppy at all. The computer is pretty much dead, except for the power supply softly humming.

I'm at a loss for reasonably solid leads to investigate further. I really hope it doesn't come down to carving up the old 1287 and soldering on a battery.

So, a couple of questions to round this up:

1. Am I wrong to assume that the Necroware 12887 can replace my old Dallas 1287 in the Compaq Deskpro 386N?
2. Did I somehow manage to order the wrong module?
3. Could the Necroware module be faulty?
4. Have anyone experienced anything like this with a Necroware 12887 replacement?
5. How would you go about trying to fix this issue?

I was saddened quite a bit when I realized I got stuck right away, when I pretty much thought I would at least have a decent shot at booting up the hard disk drive.

All input highly valued and appreciated!

Thanks in advance,
Jens

Does seem that cross-compatibility with the different model RTCs isn't always 100% - probably more a board / BIOS issue than the part itself.

Take it this is your board (version with integrated VGA)...

CPQ 386N mainboard.jpg

Yeah, it seems to be somewhat hit or miss with the replacement chips.

That is indeed the motherboard I have. Is there a known issue with this board? I read somewhere that older Compaq 286/386 can be kind of stingy when it comes to replacement for the 1287.

MikeSG wrote on 2024-02-09, 08:18:

What's wrong with soldering a new, original Dalls every ~10 years? They're lithium batteries.. no corrosion...and the board/PC has more originality value.

Actually, nothing wrong with that at all. My chip is socketed so no soldering needed. But I was under the impression these chips weren't in production any more?

Im not 100% sure, but I think that they are no longer made by the original maker. There is a large number of orginal and/or aftermarket offers available online, some with seemingly original labels some clearly remade. Prices also vary extremely. I tried a few and some work, but others dont. On the other hand, modding an original one always worked for me (although, sometimes with lots of problems - see my first post in this forum...

Socket 5 - Dallas RTC replacement gone bad )

So, in my case, I decided to rather repair the old ones instead of playing ebay battery gambling...

Repair is rather easy https://www.classic-computers.org.nz/blog/200 … attery-chip.htm

Yes repair is easy !
Yes have had issues with those Necroware replacements in the past so will not order another.
You can get good dallas chips from digikey or Quest but you have to know exactly what you have and what are the exact new replacements.
Yes with others I have modded my own many times because some old boards will just not work proper with the newer DS12887, DS12C887, DS12C887A, etc..
You have to know if the bios needs the 114bytes (non-C) or can work with 113bytes (C type) replacements for proper cmos operation....
the DS12887/DS12887A are near exact for a DS1287 plain from my experience but sometimes that does not matter.

I have about the same board (386S /20N) with a socketed dallas that was modified and now has a CR2032 glued on.
Be sure to check your caps carefully! Mine came with literally every single cap leaking.

Aui wrote on 2024-02-10, 03:15:

So, in my case, I decided to rather repair the old ones instead of playing ebay battery gambling...

This is likely the route I'm taking as well. I bought a newly made China knock-off from a guy locally who have had success with that particular batch. If nothing else, for practising before I cut into my original chip.

Thanks for sharing!

rasz_pl wrote on 2024-02-10, 04:21:

Repair is rather easy https://www.classic-computers.org.nz/blog/200 … attery-chip.htm

Thanks!

Horun wrote on 2024-02-10, 04:28:

Yes repair is easy ! Yes have had issues with those Necroware replacements in the past so will not order another. You can get […]
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Yes repair is easy !
Yes have had issues with those Necroware replacements in the past so will not order another.
You can get good dallas chips from digikey or Quest but you have to know exactly what you have and what are the exact new replacements.
Yes with others I have modded my own many times because some old boards will just not work proper with the newer DS12887, DS12C887, DS12C887A, etc..
You have to know if the bios needs the 114bytes (non-C) or can work with 113bytes (C type) replacements for proper cmos operation....
the DS12887/DS12887A are near exact for a DS1287 plain from my experience but sometimes that does not matter.

Thanks for sharing your insight! It's really valuable as I move ahead. 😀

Kouwes wrote on 2024-02-10, 07:52:

I have about the same board (386S /20N) with a socketed dallas that was modified and now has a CR2032 glued on.
Be sure to check your caps carefully! Mine came with literally every single cap leaking.

That's good advice!

The old Conner hard drive has given up on me and I will replace that with a Compact Flash Card reader and an appropriate sized card somewhere in the realms of 256 - 1024MB (I have quite a few spare ones from my photo days).

When I have everything stripped down I will clean up the machine and look for potential issues with the capacitators. Though I will say, this unit has been REALLY well cared for and it's obvious that it's been used in a really clean and controlled environment (Robotics Lab at a university).