Dallas Clock Issues \ VOGONS

Dallas Clock Issues

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First post, by bloodbath2you

Posted on 2016-01-13, 19:00

bloodbath2you Offline

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Hey! Yesterday i adquired a p133 machine with a dead VIA RTC chip (via vt8828n) pin compatible to standarf dallas rtc... the issue its the machine tells CMOS battery low even with the battery mod and also im sure the mod is correct because the pins match correctly, and when the machine chip is without the battery it posts fine but settings are all lost when reset... 😒 any ideas ? Theres any way to plug a external battery to the mobo? The mobo is a PCChips m560 p166mmx. I dont even wanna think the chip is dead because that mobo was from the first pc i ever had *sigh* ...
Here's a shot of the modified chip
http://imgur.com/C1mZuSW

Reply 1 of 6, by Callahan

Posted on 2016-01-13, 19:40

Callahan Offline

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Strange, that mobo should be equipped with dallas 12887a chip... Why don't You change it with new rtc?

Cpq: ap550(2x1G/256k), sp750(2x900/2MB), 5100(2xpII300)
TD-30 2xP166 NT 3.51
HP Vectra XU 6/200 2x PIIOD 512MB FPM Banshee
Super S2DG2@550/2MB SCSI 15k V5 5500
P4T533-C P4 3,06 Ti4600
Dell T700r @P3-700 V3 3500
PR440FX-2x PIIOD Voodoo 4500 PCI r320 CT1920

Reply 2 of 6, by Tetrium

Posted on 2016-01-13, 19:41

Tetrium Offline

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edited: Seems yours is already modded.

Whats missing in your collections?
My retro rigs (old topic)
Interesting Vogons threads (links to Vogonswiki)
Report spammers here!

Reply 3 of 6, by bloodbath2you

Posted on 2016-01-13, 19:55

bloodbath2you Offline

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Rank: Newbie
Posts: 26
Joined: 2015-09-09, 01:11

Callahan wrote:
Strange, that mobo should be equipped with dallas 12887a chip... Why don't You change it with new rtc?

The vt8828 is equivalent, i have no way to find one of these here in chile, months ago saw one guy selling these as new but his announce no longer exists, also i dont have $$$ for it.

I have a question, in the datasheet pin 16 is NC but not negative, ive tried soldering the negative battery pin to GND pin 12, should this have an influence? Because maybe due propietary design of the chip the PIN 16 was just removed making no contact with the external battery from the original mod... or may i be wrong?

Another thing, or just maybe all batteries that i've tried are dead... but some of them were working good on other pc's... help 🙁

At the begining i thought it could be easy but all went to shit...

Reply 4 of 6, by Callahan

Posted on 2016-01-13, 21:02

Callahan Offline

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Joined: 2014-04-10, 15:59
Location: Kielce Poland Polska

I bought five dallas 12887a chips for 5$ with shipping on aliexpress 😀
http://www.aliexpress.com/item/DS12887A-OEC12 … 2428102352.html
Look here for a tip with dallas mod:
http://www.mcamafia.de/mcapage0/dsrework.htm
http://www.classic-computers.org.nz/blog/2009 … attery-chip.htm

Reply 5 of 6, by Windows9566

Posted on 2016-01-14, 01:12

Windows9566 Offline

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Location: USA

my packard bell has a cr2032 battery, not a dallas chip

R5 5600X, 32 GB RAM, RTX 3060 TI, Win11
P3 600, 256 MB RAM, nVidia Riva TNT2 M64, SB Vibra 16S, Win98
PMMX 200, 128 MB RAM, S3 Virge DX, Yamaha YMF719, Win95
486DX2 66, 32 MB RAM, Trident TGUI9440, ESS ES688F, DOS

Reply 6 of 6, by bloodbath2you

Posted on 2016-01-14, 22:16

bloodbath2you Offline

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Rank: Newbie
Posts: 26
Joined: 2015-09-09, 01:11

Heey guys! Thanks for the help, i've found the mod and the chip were right, all of the batteries that i tested were just dead then used a new one and worked perfectly

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