DS12887 pcb substitute with battery

[Jon Elson]

On 01/23/2017 04:57 AM, allison wrote:
> On 01/22/2017 02:46 PM, Chuck Guzis wrote:
>> On 01/22/2017 10:57 AM, allison wrote:
>>> I don't know about most people but this solution has been around for
>>> decades.
>>>
>>> I locate the battery on the failed part with a small magnet, then
>>> grind the epoxy down to it then pick it out with a sharp pointed
>>> tool.  Once I expose the connection point I older two wires then
>>> epoxy a small coin-cell holder in that spot and it s done.  I've done
>>> this more times than I care to count and its effective and the
>>> replacement battery some over 10 years old now have not failed.  But
>>> just in case I have a bag of NOS replacements (and pulls from
>>> socketed boards) all with dead batteries from age.  There is no magic
>>> to this.
>> It's worth noting that the original post was about fabricating a
>> replacement using the DS12885A RTC chip.  However, most old PCs used the
>> DS1285 RTC (inside of a DS1287  module).  The DS12885A is supposed to be
>> drop-in compatible with the DS1285, but apparently, in some cases is not.
>>
>> So there's logic in reworking the old DS1287 modules, as the DS1285 chip
>> is long out of production--you'll most likely have to be content with
>> pulls or the occasional NOS lot.
>>
>> --Chuck
> I haven't seen that version for a while.  The later are fully versions
> are epoxy filled.
> Same for the MT48T part, same fix.
>
> The problem with NOS parts is manufacture date.  Some are really old.
>
>
Well, it doesn't really matter.  If you can find one of the 
"really old" ones, the battery can be replaced and you are 
good for 5 years or so.  There must be TONS of these old 
clock/RAM chips out there, and somebody must have saved a few.

Jon