23 Jan
2017
23 Jan
'17
9:04 a.m.
On 01/23/2017 04:57 AM, allison wrote:
On 01/22/2017 02:46 PM, Chuck Guzis wrote:
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
On 01/22/2017 10:57 AM, allison wrote:
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.
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