Is my CMOS battery failing on P55T2P4?

[J. H. Meinema]

Hello, Michael...

> My system clock seems to not be keeping the correct time. It's just started, so I don't
> know exactly how far out on average but isn't this one of the first signs that the battery
> is going?
>
> If that's the case can I replace the battery?

A serious problem i see... yep... the battery is leaking his power away.... or in other words,
the battery is almost to it's end... It's safe to say that you can change the old battery for
a new one.. do mind that you will try to get a exact same kind/type of battery back.
--
Anne Meinema

j.me...@chello.nl <-- for fast reply's

vipe...@hetnet.nl <-- for slow reply's

http://go.to/meinema/

[Gerhard Miksic]

I believe your suggestion is right, it seems that the CMOS battery is ging to fail because of
it's internal lithium battery is coming to it's end.
Unfortunately the DALLAS RTC chip is soldered onto the board, not socketed.
If you want to exchange it, you have to have good soldering skills.
Furthermore the chip, at least the ones used on my 3.1 T2P4s (DS12B887), are not being built
anymore.

Because of this reason, I contacted DALLAS Semiconductor some time ago, my specific questions
was answered in a very professional way.

Quoted from a mail I received from Lee Cash/Dallas Semiconductor regarding my exchangeabitily
question:

S T A R T QUOTE

Dear Mr. Miksic,

The DS12B887 Real Time Chip was designed as a variation of the DS12887A. The only difference
between the two devices is related to the function of pin 21 (RAM Clear or RCLR). In the
DS12887A, the RCLR pin will function to clear the user RAM only when the device is in battery
backup mode. In the DS12B887, the RCLR pin has the same function, but will only work when VCC
is applied. On the DS12887 pin 21 is a no connect.

The RCLR function is designed to clear the CMOS RAM memory. This function was put in when
people began putting paswords in the operating system and needed a place to store the password
while the power was turned off. Users have a tendency to forget passwords, so the system
designers needed a back door to clear the memory and regain access to the system. I can not
tell how this function has been implemented in your case. The most common arrangements
involved using a jumper on the motherboard to ground the RCLR pin and clear the memory.

I would suspect that either the DS12887A or DS12887 would work. In the case of the DS12887,
there is no external way to clear the memory. In the case of the DS12887A the RAM memory can
be cleared by taking pin 21 low, but only when Vcc is off. Therefore, as long as you do not
have need for the RAM Clear function, you should be able to replace your DS12B887 with either
the DS12887 or DS12887A.

The DS12C887 includes a century counter to make it Y2K compliant. Unless you also replace
your BIOS, your system will not access the century bit in the DS12C887, so I would not bother
with this device. However, all of its other features are the same as the DS12887.

The data sheets for the DS12887, DS12887A, and DS12C887 are still available at:

http://www.dalsemi.com/DocControl/PDFs/pdfindex.html

I trust this will be of some help.

E N D QUOTE

Personal note: This IS really good customer support. Period.

Well, the DS12887A itself is also out of production now, but it is still available here and
there. You may want to look for it in your local electronics shop (If you're unsuccessful
finding it locally, I'll be glad to help you with the European address, where I got mine
from).

Another possible way may be of some interest for you, though I did not do it by myself:
As the chip itself consists of the RTC chip, a lithium battery on top of it and a plastic case
surrounding it, filled with some kind of epoxy material, someone has suggestd a method ripping
off the plastic case, exchanging only the lithium battery. Theres a Web page with a more
detailed description somewhere out there though I do not have the link ready.
As far as I remember, he used a sharp knife to cut some part of the plastic case away, another
method may be to use a soldering iron instead, to "melt it away".

Hope it helps!

Good luck
Gerhard

Michael Goodman schrieb:

> My system clock seems to not be keeping the correct time. It's just started, so I don't
> know exactly how far out on average but isn't this one of the first signs that the battery
> is going?
>
> If that's the case can I replace the battery?
>

> thanks,
>
> mike
> Jester
>
> if replying to me directly make sure to edit my anti-spam email
> address.

[Wayne Monteath]

No, there are not, the only "safe" thing to do is replace the entire RTC
module.

The RTC is about $12.00 CDN and can be replaced by anyone who knows the
precautions of how to solder a multi-layer PCB board in less than 10
minuets.

Wayne Monteath

Michael Goodman <trek_del...@pcola.gulf.net> wrote in article
<q31vfsso031ifsd49...@4ax.com>...
> Are there any connections for an external battery?
>

[Peter]

On Thu, 20 Apr 2000 14:37:45 +0200, Gerhard Miksic
<gerhard...@nospam.please.at> wrote:
>Unfortunately the DALLAS RTC chip is soldered onto the board, not socketed.
>If you want to exchange it, you have to have good soldering skills.

Thanks a lot for the info! Do you know what are the voltage of the
internal lithium cell is?
Cheers Peter

[Gerhard Miksic]

If my memory serves me correctly it's 3 Volts - but you certainly will
find that out by yourself if you open it up (as your question suggests)
;-)

Regards
Gerhard

[Gerhard Miksic]

Hi,

I found the link(s) to how to exchange only the lithium battrey of the RTC.

In English: http://www.geocities.com/markuskauer/rtc.html

In German: http://www.geocities.com/markuskauer/rtc_de.html

Hope it helps!

Best regards
Gerhard

Gerhard Miksic schrieb:

--
"You know, how is The Force like duct tape? Answer: it has a light side,
a dark side, and it holds the universe together."

-- Larry Wall (Open Sources, 1999 O'Reilly and Associates)

[Wayne Monteath]

Interesting, but, anyone attempting this kind of surgery already has the
necessary soldering skills to remove the RTC, install a socket on the
motherboard and then insert a new clock chip.

Just for a lark, I just tried to remove the RTC case top, with the chip
still on the board, with a heat gun. The solder on the pins melted before
the top came off and the RTC came out of the board quite easily.

Wayne Monteath

Gerhard Miksic <gerhard...@gpm.at> wrote in article
<3904DFD4...@gpm.at>...

[Gerhard Miksic]

I did not and do not recommend this method, but as someone seemed to be
interested I wanted to provide a link.

Also keep in mind, that both the DS12B887 and DS12887A are out of production
now and that the recent "C" model may not work correctly in the T2P4, so that
kind of "surgery" will probably be the last chance to prolong this
motherboard's life in the furture...

Regards
Gerhard

Wayne Monteath schrieb: