Best place to buy a Dallas DS12887A?

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Re: Best place to buy a Dallas DS12887A?

Postby exxos » Fri May 20, 2016 3:07 pm

I've had to make the PCB at a angle to clear the top of the combel as the battery terminals sticking below the board could touch the top of the IC and lift the board up higher.

From my workings so far there is about 5mm clearance between the top of the battery and the top of the keyboard pillar.. I think that's pushing it a bit.. Its hard to tell from the image how much space of the pillar is sticking above the shelling. I guess worst case would be it may lift the shielding up a couple of mm, that probably wouldn't be a problem really anyway.

I will have another look at some batteries, though possible the only solution would be to use something like a twin AA type battery pack and just drill a small hole to poke the wires though to the PCB...

There are lithium batteries like the "coin style" ones, but I'm trying to avoid those because of shipping problems. Its why I had to stop shipping the Dallas RTC's overseas :( and its typical the lithium ones are the only ones likely to fit.

So there is the original option of just using a normal non-rechargeable cell. Or look into the super caps some more...

Something like this would fit.. Doesn't even have to take up space on the board, can be soldered and just double sticky taped on the motherboard or something.

Its 5F, so assuming 1F lasts 6 months, then it would last a couple years between charges easily.

2148512-40.jpg


In anycase, if someone can tell me the height of the pillar above the shielding then I can see if it will fit or not. If not then the only option is to basically do the same board as arne did, though I personally would solder a super cap on there. If there are 2 pads for "power" then people can hook in whatever they want.
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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Fri May 20, 2016 4:06 pm

Would still prefer the non-rechargeable cell option that sits below all the metal shielding, but here's the photo I think you want of the pillar

2016-05-20 17.02.18 (Custom).jpg
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Re: Best place to buy a Dallas DS12887A?

Postby exxos » Fri May 20, 2016 4:37 pm

catmando wrote:Would still prefer the non-rechargeable cell option that sits below all the metal shielding, but here's the photo I think you want of the pillar


Thats awesome thanks! So likely 1mm to spare!

I can do 2 versions anyway, one basically the same as arne's layout, then another one which can take this small nimh battery. I was going to use the SMT chip, but if I go with the DIP version then people can build this themselves. So the only thing I need to do is find some battery sockets..
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Re: Best place to buy a Dallas DS12887A?

Postby exxos » Fri May 20, 2016 5:57 pm

The board is offset to miss the top of combel IC. This design has pads for the CR2032 and the nimh battery I want to use.

IMG_20160520_185311.jpg
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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Fri May 20, 2016 6:16 pm

exxos wrote:The board is offset to miss the top of combel IC. This design has pads for the CR2032 and the nimh battery I want to use.

IMG_20160520_185311.jpg


Looks good. I'd buy one (or more)

I do like the neatness of the SMT version though, I don't suppose it would be possible to produce both?
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Re: Best place to buy a Dallas DS12887A?

Postby exxos » Fri May 20, 2016 6:23 pm

catmando wrote:
Looks good. I'd buy one (or more)

I do like the neatness of the SMT version though, I don't suppose it would be possible to produce both?


Possible, though do you mean where the SMT is under the RTC IC and battery on top ?... as I would suspect that would be to high ?

The layout I did is similar to Arne's one using the DIP IC. Using SMT there is just making harder soldering.
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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Fri May 20, 2016 6:30 pm

exxos wrote:
catmando wrote:
Looks good. I'd buy one (or more)

I do like the neatness of the SMT version though, I don't suppose it would be possible to produce both?


Possible, though do you mean where the SMT is under the RTC IC and battery on top ?... as I would suspect that would be to high ?

The layout I did is similar to Arne's one using the DIP IC. Using SMT there is just making harder soldering.


Judging by this picture the SMT version looks no higher than the original Dallas chip, if so may even be able to install a slimline socket too

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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Fri May 20, 2016 6:37 pm

I have a Falcon where I cut out a square in the metal shielding for a replacement Dallas chip in a non-slimline socket so I can measure the depth from the shielding on the sloping part to the board.

On the long front edge of the chip a safe height from the board would be 9mm
On the long back edge of the chip a safe height from the board would be 13mm

There's a +1mm margin on those measurements

2016-05-20 19.40.38 (Custom).jpg
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Last edited by catmando on Fri May 20, 2016 6:42 pm, edited 3 times in total.
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Re: Best place to buy a Dallas DS12887A?

Postby exxos » Fri May 20, 2016 6:37 pm

OK, I will do that style layout aswell.
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Re: Best place to buy a Dallas DS12887A?

Postby exxos » Fri May 20, 2016 7:26 pm

catmando wrote:Judging by this picture the SMT version looks no higher than the original Dallas chip, if so may even be able to install a slimline socket too



20160520202256.jpg
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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Fri May 20, 2016 7:44 pm

exxos wrote:
catmando wrote:Judging by this picture the SMT version looks no higher than the original Dallas chip, if so may even be able to install a slimline socket too



20160520202256.jpg


Haha. nice :D
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Re: Best place to buy a Dallas DS12887A?

Postby Brume » Wed Jun 01, 2016 12:03 pm

Thanks to all for your replies :)
The projects by Arne & Exxos seem very interesting.
I'll try them on one my Falcon, but I'd like also to try to replace the DS12887A by a new one on the other machine. I'll order two new chips on the link given by bartek030, the site seems to be reliable (thanks for it bartek030).
Will let you know if i success the replacment. First I do such a thing : it may look easy for most of Falcon owners, but not for me ;)

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Re: Best place to buy a Dallas DS12887A?

Postby Brume » Sun Jun 12, 2016 9:57 am

I received Dallas DS12887+ last week from TME (very fast service).
A friend of mine, who we can consider as a profesionnal in electronic, replaced it. The job seems to be very well done, I can take some pictures if required.
But there's still the same issue: the Falcon runs but there's a blank image on screen. Nothing else happens.
I tried to replace the RAM and checked keyboard and floppy drive = same issue.

I have one question: there was previously a MK48T87B by Thomson in my Falcon. Did I have to replace the chip with the same model?

Thanks for any kind of help. I'm lost...

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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Sun Jun 12, 2016 10:39 am

Brume wrote:I received Dallas DS12887+ last week from TME (very fast service).
A friend of mine, who we can consider as a profesionnal in electronic, replaced it. The job seems to be very well done, I can take some pictures if required.
But there's still the same issue: the Falcon runs but there's a blank image on screen. Nothing else happens.
I tried to replace the RAM and checked keyboard and floppy drive = same issue.

I have one question: there was previously a MK48T87B by Thomson in my Falcon. Did I have to replace the chip with the same model?

Thanks for any kind of help. I'm lost...


Did the Falcon boot normally before you replaced the chip?
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Re: Best place to buy a Dallas DS12887A?

Postby Brume » Sun Jun 12, 2016 11:02 am

No, it didn't. It had the same issue before I replaced the chip= white screen.

But: it booted normally when I put my CT060 inside the machine.
When I removed the CT060 (which comes from my other Falcon), it refused to boot and still displayed a white screen. That's why I supposed it came from the NVRAM and ordered a new one.

I'm just coming to do more attempts. The hard drive starts (we can hear it), the fan starts too, led on the keyboard is OK. But always the same white screen.

edit: some photos of the job... can't see anything wrong on it, but I probably need expert eyes

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Re: Best place to buy a Dallas DS12887A?

Postby exxos » Sun Jun 12, 2016 11:31 am

Assume you are putting the jumper link back on the motherboard when you remove the CT60 ?
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Re: Best place to buy a Dallas DS12887A?

Postby Brume » Sun Jun 12, 2016 12:02 pm

Which Jumper, exxos?

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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Sun Jun 12, 2016 12:13 pm

Brume wrote:Which Jumper, exxos?


This jumper

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Re: Best place to buy a Dallas DS12887A?

Postby Brume » Sun Jun 12, 2016 1:22 pm

You make my day, guys!

How could I forget to put the jumper?

Now it works like a charm!

Thank you very much, my Falcon relives :D

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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Wed Jun 29, 2016 9:45 pm

exxos wrote:
catmando wrote:Judging by this picture the SMT version looks no higher than the original Dallas chip, if so may even be able to install a slimline socket too



20160520202256.jpg


Any progress on these boards Exxos? :shrug:
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Re: Best place to buy a Dallas DS12887A?

Postby exxos » Wed Jun 29, 2016 10:13 pm

catmando wrote:Any progress on these boards Exxos? :shrug:


I've not had time to work on it with working on the STE boosters, but I did order some parts like the battery socket and super cap. I've just got that many projects on the go at the moment its unreal. It will get done at some point, but I really can't say when. Currently I've found a RAM issue on the STE which seems to be a built in design problem, so I am looking into that as its more important IMO.
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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Wed Jun 29, 2016 10:17 pm

exxos wrote:
catmando wrote:Any progress on these boards Exxos? :shrug:


I've not had time to work on it with working on the STE boosters, but I did order some parts like the battery socket and super cap. I've just got that many projects on the go at the moment its unreal. It will get done at some point, but I really can't say when. Currently I've found a RAM issue on the STE which seems to be a built in design problem, so I am looking into that as its more important IMO.


Cool no worries and no rush either. Cheers
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Re: Best place to buy a Dallas DS12887A?

Postby Atari030 » Wed Jun 29, 2016 11:22 pm

Yup, I have ten years to worry about it. ;-)

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Re: Best place to buy a Dallas DS12887A?

Postby exxos » Tue Jul 12, 2016 12:29 pm

The PCB is actually done with this, I could get a couple made if someone wants to volunteer to try one out. Though It would be the PCB only and the person needs to be good at soldering because of the SMT IC.

Problem for me I am maxed out work wise, and just can't take on anymore projects currently :( So while the PCB is designed, I could send a couple out if people want to get parts and built it themselves and give it a try out. Would save me some work and would help move the project along.
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Re: Best place to buy a Dallas DS12887A?

Postby catmando » Tue Jul 12, 2016 2:52 pm

exxos wrote:The PCB is actually done with this, I could get a couple made if someone wants to volunteer to try one out. Though It would be the PCB only and the person needs to be good at soldering because of the SMT IC.

Problem for me I am maxed out work wise, and just can't take on anymore projects currently :( So while the PCB is designed, I could send a couple out if people want to get parts and built it themselves and give it a try out. Would save me some work and would help move the project along.


Sounds good to me, I'd be up for that
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