Dallas RTC Replacement \ VOGONS

Dallas RTC Replacement

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First post, by wiretap

Posted on 2019-06-28, 18:15

wiretap Offline

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I replaced the dead TH6887A RTC on my Biostar MB-1433 today with a new Dallas DS12877A. Very easy, only takes about 15 minutes. I hope this short little guide helps you. 😎

Here's the motherboard with the existing (dead) RTC installed on the left-middle side.

Picture of the newly manufactured (2018) Dallas chip, about $10 from Newark:

First, I placed the motherboard vertical with the RTC on my right, and the soldered rear side on my left. I set my hot air pencil to the melting point of the solder, then slowly worked over the pins until everything was melted. Then I used a pair of needle nose plyers to pull the RTC off the motherboard. It comes out very easy with little effort if you have all the solder melted.

Now to clean up the holes which are full of solder. I held the motherboard in the same position, with my soldering iron in my right hand and solder sucker in the other. Heat up one pin hole at a time, and suck the solder out the opposite side. Repeat for all the pin holes. This would be easier if you have a vacuum pump desoldering tool, and would also eliminate the above step. I am cheap so I did it the "hard" way. Nice and clean now:

Next, put a DIP socket into the RTC location to facilitate easy replacement 10+ years from now. Solder it in place.

Finished product:

My Github
Circuit Board Repair Manuals

Reply 1 of 5, by keropi

Posted on 2019-06-28, 18:25

keropi Offline

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very nice and clean job kudos

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Reply 2 of 5, by SSTV2

Posted on 2019-06-28, 18:59

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To avoid such whoopsie-daisies as that melted ISA slot, I use 2-3 layers of adhesive paper tape on any surrounding parts that can be easily damaged by a soldering iron. It insulates heat long enough for you to notice, that soldering iron is touching something it shouldn't.

Now decapsulate that old RTC module with a heatgun and repurpose RTC chip (upward bent pins can be bent back only once) 😈

Reply 3 of 5, by SirNickity

Posted on 2019-06-28, 20:31

SirNickity Offline

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That's the truth. The pins on those things suuuuuuuuck.

Well, I guess now that you have a working RTC, you won't be welcome on that Norwegian island anymore. 😁 But you will be able to save your CMOS settings, which is nice.

Reply 4 of 5, by MMaximus

Posted on 2019-06-28, 21:13

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Many thanks for posting this - I plan on doing RTC chip replacement on a few boards over the summer, and having never done any soldering or desoldering work before, any help is greatly appreciated!

Can I ask what you used to hold the board vertically during the procedure?

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Reply 5 of 5, by wiretap

Posted on 2019-06-28, 23:18

wiretap Offline

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MMaximus wrote:
Many thanks for posting this - I plan on doing RTC chip replacement on a few boards over the summer, and having never done any soldering or desoldering work before, any help is greatly appreciated!

Can I ask what you used to hold the board vertically during the procedure?

I just sandwiched it between two books that were large/heavy enough to hold it in place. One being The Doom Programming Gurus book. 🤣

My Github
Circuit Board Repair Manuals

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