Weird motherboard behaviour after Dallas RTC replacement \ VOGONS

Weird motherboard behaviour after Dallas RTC replacement

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First post, by Bernkastel7734

Posted on 2021-11-29, 21:39

Bernkastel7734 Offline

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I was trying to replace a rtc chip on ASUS P/I-P55TP4-XE. Desoldered the chip and soldered socket for future needs. After soldering the socked I tried if it works, I've used modified rtc chip with cr battery mod I know is working ( tested on other motherboard), it worked fine and kept settings. Then I modified the chip that was originally on the board. And now the fun begins. I didn't keep settings with new chip. So I went back to the chip it was working with earlier. And now it does boot once every 20-30 time I try to boot it. I have POST diagnostic card and the board is supplied with Award Pnp/PCI BIOS. It freezes at 'Verify CMOS Read/Write' thing. I thied to use unmodified dallas chip, and these two chips I have tried earlier. It seems to be random when it boots and when it freezes. Any idea whats going on?

Reply 1 of 6, by snufkin

Posted on 2021-11-29, 21:45

snufkin Offline

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Pictures of the socket and back of board? Maybe there's an iffy joint or trace near the Dallas chip, and something got disturbed when you swapped chips?

Reply 2 of 6, by Horun

Posted on 2021-11-29, 23:28

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I agree snurfkin ! Most likely a solder bridge or cold joint.
What is the EXACT model of the Dallas chip ? My P55TP4-XEG has a soldered DS12887A.
The jumper JP13 can clear the CMOS in the Dallas but also can cause it to not boot because it is shorting pin 21 of the Dallas chip, my guess is that you have some solder joint that is doing similar..

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 3 of 6, by majestyk

Posted on 2021-11-30, 09:55

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The ASUS P/I-P55TP4-XE comes with the Dallas "DS12887A", if you replace it with the more familiar "DS1287" the CMOS settings are being reset at every boot resulting in a "CMOS corrupt" message every time.

Reply 4 of 6, by Bernkastel7734

Posted on 2021-11-30, 21:43

Bernkastel7734 Offline

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So, re-soldered all the joints and have noticed that one trace was ripped out, dunno if it have happened during first soldering or second one, will repair that trace and see if it was the culprit. And yes, it was supplied with ds12887A chip

Reply 5 of 6, by Bernkastel7734

Posted on 2021-12-01, 09:04

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Fixed that broken trace, and used ds12887A and it seems to work again

Reply 6 of 6, by Horun

Posted on 2021-12-01, 14:34

Horun Offline

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Bernkastel7734 wrote on 2021-12-01, 09:04:

Fixed that broken trace, and used ds12887A and it seems to work again

Great !!

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

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