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Twinhead TH6887A Rework Success

Hello all...

I'm reporting success with two more Dallas DS1287/12887 clones. While
in Kentucky, I grabbed a number of clock modules, most of them marked
TH6887A. There was also one Benchmarq BQ3287 that I ran across while
going through the box they landed in.

The TH6887A is supposedly a clone of the Dallas DS12887 made by
Twinhead International Corporation. The construction of this module is
only slightly different from the Dallas Semiconductor products.
Whatever the case, it takes well to being reworked with external
batteries and is a drop-in replacement for the DS1287 in any PS/2 that
uses one. (Tested on a 55SX, should work on others.)

Someone already did a modification to a TH6887A (found the result in a
web search) but the page is long gone and has not been archived.

I also took the opportunity to carve open the Benchmarq BQ3287 clock/
NVRAM module. It too appears to be reworkable. The battery contacts
are barely underneath the potting resin, and are easily exposed. More
as I do it.

I can say that the BQ3287 has an extra pin on it that you will need to
remove, or the result will be a module that becomes extremely hot when
installed in a PS/2. Someone (can't find the original thread) told me
that it has to do with the normally unused pins being set to +5V in a
PS/2.

Peter: if you post this on your site, I can also offer a good link for
my DS1387 page (which still points to greyghost.dyndns.org on your
rework page). It is now http://greyghost.mooo.com/ds1387rework/ .

William
0
William
11/16/2009 8:36:06 PM
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Hi William !

> I can say that the BQ3287 has an extra pin on it that you will need to
> remove, or the result will be a module that becomes extremely hot when
> installed in a PS/2. Someone (can't find the original thread) told me
> that it has to do with the normally unused pins being set to +5V in a
> PS/2.

Vaguely recall the thread and the module as well.
As far as I can tell the Benchmarq stuff is not fully Dallas compatible.
They're Texas Instruments now IIRC.

> Peter: if you post this on your site, I can also offer a good link for
> my DS1387 page (which still points to greyghost.dyndns.org on your
> rework page). It is now http://greyghost.mooo.com/ds1387rework/ .

I would like to update my page for the proper link as well as leaving a 
comment on the "more or less compatibles" to be found on your page. That 
may extend the number of people finding help ...

I'm going to add a link to a fellow in New Zealand, who also reworked 
the DS1287:
http://www.classic-computers.org.nz/blog/2009-10-10-renovating-a-dallas-battery-chip.htm


-- 

Peter from Germany
http://www.mcamafia.de
0
Peter
11/16/2009 9:22:24 PM
Hi Peter,
> I'm going to add a link to a fellow in New Zealand, who also reworked the 
> DS1287:
> http://www.classic-computers.org.nz/blog/2009-10-10-renovating-a-dallas-battery-chip.htm
     I know Tezza from the Vintage Computers Forum 
(vintage-computer.com/vcforum)...
                        David
                        David@IBMMuseum.com 

0
David
11/17/2009 5:12:53 PM
Hi!

> I would like to update my page for the proper link as well as leaving a
> comment on the "more or less compatibles" to be found on your page.
> That  may extend the number of people finding help ...

Here's a page that I whipped up about the TH6887A module.

http://greyghost.mooo.com/th6887a/

The one I have finished so far seems to work perfectly well in a 55SX. I am
not sure whose IC it would be based on, or if Twinhead really even made it.

William


0
William
11/19/2009 7:20:06 AM
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