Brickpad wrote:

Is the 12885 compatible with the 1287/ 12887 though? The date code on that chip shows 1995, and I think that is a surface-mount chip and not a through-hole.

Oh I thought you were referring to components for assembling the board, not the component the boards are meant to replace. You can search Aliexpress for DS12887 too, I remember seeing some at about $3 per piece in lots of 5-10. The one thing about them though is you can't be sure how long they have been in storage and if the embedded battery is any good anymore.

as long as you understand the 12885 does not have 100% functionality of 12887! (no century byte). on 85 its ram. if you know it wont be needed, or you know, we wont need to increment century 😉 that it does not matter much.

BloodyCactus wrote:

as long as you understand the 12885 does not have 100% functionality of 12887! (no century byte). on 85 its ram. if you know it wont be needed, or you know, we wont need to increment century 😉 that it does not matter much.

Correct, however I've never seen a computer using said century byte. In that case, the only real difference lies in the 12885 just not having a battery. 😉

Brickpad wrote:

Thanks for the update! Is there a minimum order quantity? I will probably order 3-5 of them for projects and spares if / when th […]
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Maeslin wrote:

Brickpad wrote:

Well there's this. https://oshpark.com/shared_projects/DgExxcyH

It looks like it can still be ordered.

This is the newer version: https://oshpark.com/projects/NwcVatSK It sits ~1.6mm lower than the first version.

Thanks for the update! Is there a minimum order quantity? I will probably order 3-5 of them for projects and spares if / when they're available.

[edit]

I can assemble these myself if it's possible to order all the parts as one package?

OSHPark only does PCBs, you'd have to find a separate source for parts. I usually get mine from digikey or similar for most components. The 12885s I got from aliexpress.

OSHpark works in batches of 3 PCBs. You pay for the square footage of one board, you get 3 of them. I still have plenty in stock but I'm only back on land for a few short days and heading offshore again in under a week until the end of September (North Pole, so no TV and no Internet access either). This unfortunately doesn't leave me time to prepare shipments. 🙁

I placed this in an another thread, but I preferred the Houston RTC as there is no epoxy inside. Sadly, it is not compatible with the Dallas RTC pinout. It was very simple to change the CR1225 inside, just had to drop by Batteries Plus to get the tabs spot welded onto the new battery, which they did for free.

It would be great if the Dallas chip could be purchased without the cap or epoxy. All one would have to do it bend the pins upward and attach battery.

I would definitely be interested. I toasted an IBM PS/1 system trying to mod the chip and was lucky enough to find a second /exactly clone/ today. I'm ordering one from China, no more of that crap.

Glad to see that this is still alive 😀

I ordered six PCBs from OSH Park in mid-September (https://oshpark.com/shared_projects/NwcVatSK). They arrived today and as you can see, they are completely destroyed and I can throw them in the garbage.

How did that happen?

They don't seem destroyed. Sure there is some remaining copper that you may need to trim, but it followed what I see on the board view. It sawed through the holes as expected.

it matches your gerbers, your board outline goes through the holes. they did what you told them to do.

Ouch! And I was going to order some of these, but I forgot. I know nothing about PCB design, so I would not have thought about checking the file or even looking at the PNG for errors.

BloodyCactus wrote:

it matches your gerbers, your board outline goes through the holes. they did what you told them to do.

I thought it was Maeslin's design, not Half-Saint's.

Yes, design is Maeslin's and I saw photos of properly done PCBs so didn't think to look.

This guy ordered them from OSH Park as well and they look fine to me:
http://www.8bity.cz/2014/bateriova-nahrada-rt … s12887-mk48t87/

There are two versions of the PCB, if you look here: https://oshpark.com/profiles/maeslin

I thought V3 was somehow improved but I'd say that it's in fact buggered and should never have been shared. There's no room to mount the specified battery holder on top of the PCB because the holder covers the solder pads.

I'll risk it and order a batch of the first version of the board. Hope it's not another $7.80 wasted.

Half-Saint wrote:

There's no room to mount the specified battery holder on top of the PCB because the holder covers the solder pads

I dont understand what you mean. It looks fine to me. Some of the silk screen goes over the through hole, but you can see in the one the other guy made it fits fine

http://www.8bity.cz/wp-content/uploads/2014/1 … ront_Martin.jpg

I would clean up the edges a bit and just build up the boards you got, they will work fine.

the only differences I see (a quick look) are the board outline goes through the edge PTH, and the PTH have been made bigger, but they are in the same place if you look at the outlines. there is more exposed copper on the v3 board for the edge PTH.

So is anyone making / shipping these at the moment? Sounds like they would be a perfect drop in replacement for the dying ones in the Atari Falcon, which originally used either the DS12887, or MK48T87B-24 chip.

Even a better solution then the one I ordered from someone, which basically makes it sort of lean out over one of the other chips.

leech wrote:

So is anyone making / shipping these at the moment? Sounds like they would be a perfect drop in replacement for the dying ones in the Atari Falcon, which originally used either the DS12887, or MK48T87B-24 chip.

Even a better solution then the one I ordered from someone, which basically makes it sort of lean out over one of the other chips.

I'll try to assemble mine and we'll see how it goes.

Half-Saint wrote:

I ordered six PCBs from OSH Park in mid-September (https://oshpark.com/shared_projects/NwcVatSK). They arrived today and as you can see, they are completely destroyed and I can throw them in the garbage.

The castellated edges are intentional, but they can need a bit of cleanup due to how OSHPark makes them (board edge cutting through the center of a hole). I'll post a picture of the assembled 'V3' PCB later. The only differences between the original and newer version is that the newer doesn't need pins removed out of the socket, sits 'lower' and is slightly narrower. I personally also find assembly easier, despite possibly having to clean up some boards.

Sorry for the slow reply btw, I was at sea from June to until a few weeks ago and all my equipment is still on the ship.

Maeslin wrote:

Half-Saint wrote:

I ordered six PCBs from OSH Park in mid-September (https://oshpark.com/shared_projects/NwcVatSK). They arrived today and as you can see, they are completely destroyed and I can throw them in the garbage.

The castellated edges are intentional, but they can need a bit of cleanup due to how OSHPark makes them (board edge cutting through the center of a hole). I'll post a picture of the assembled 'V3' PCB later. The only differences between the original and newer version is that the newer doesn't need pins removed out of the socket, sits 'lower' and is slightly narrower. I personally also find assembly easier, despite possibly having to clean up some boards.

Sorry for the slow reply btw, I was at sea from June to until a few weeks ago and all my equipment is still on the ship.

Hi Maeslin,

what software did you use to design the PCB? Personally I'd prefer a PCB that hasn't got castellated edges even, if that means adding a couple of milimeters to the total width of the board. I'll try to assemble one PCB as soon as possible and see for myself how crowded it is. It looks like the battery socket eats into the solder pads that are on the edge.

Cheers

Half-Saint wrote:

Hi Maeslin,

what software did you use to design the PCB? Personally I'd prefer a PCB that hasn't got castellated edges even, if that means adding a couple of milimeters to the total width of the board. I'll try to assemble one PCB as soon as possible and see for myself how crowded it is. It looks like the battery socket eats into the solder pads that are on the edge.

Cheers

I have access to Altium Designer. That's what I did the design with.

Unfortunately, that outer edges of the battery socket will go over the solder pads for both versions. It's just the narrowest battery holder I could find in CR1220 with a 'from the top' battery loading and the outer pads can't be made wider since it wouldn't actually fit in a DS12887 socket anymore. The castellations allow soldering 'from the sides' so it simplifies mounting. For the original board, it's necessary to cut the carrier pins flush with the top of the pcb (not to mention remove a few of them) and do a very clean soldering job with no 'bump' profile before mounting the battery holder in place. I should be able to upload V3 assembly pictures tonight.

Took longer than expected, but here are assembly pictures. Sorry for the picture quality, those were taken from my phone. The soldering job is also not the best; my good tools are still on the ship and all I had on hand was a crappy 'radio shack special' and a few inches of leftover solder.

bare board:

1. Install 32.786kHz crystal (a drop of superglue can help secure the crystal body to the pcb):

2. Install battery holder:

3. Flip over and install DS12885 IC:

4: Remove center crosspiece of socket (soldering iron + fine blade work best):

5: Trim pins of socket (on the 'stub' side, not the other side):

6: Fit crenelated board on socket. The 'stubs' can be used to scrape off any copper residue in crenelations.

Side view of board on socket

7. Solder crenelations to socket pins. The crenelations allow soldering 'from the sides' instead of 'from the top'. Copper-less crenelations are 'no connect'

Opposite side view of soldered board

edit: For some it might make things easier to mount the crystal and battery holder (steps 1 & 2) after mounting the pcb to the socket (step 7)

That's a really neat solution (but fix that one blobby corner pin)!