OT- Replacing 24 pin soldered motherboard battery ? (Pic)
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    Default OT- Replacing 24 pin soldered motherboard battery ? (Pic)

    Only 2 traces on backside connect to pins. Presume the other pins connect topside...so wondering how tricky will the desoldering and soldering of this be ? I have top notch Hakko equipment and lots of IC desoldering experience (with pins intact) but never with traces this small.

    348ee706-4ac0-4fdf-aeb1-3e330e9cc4ca.jpg 129f6b74-c3c7-486d-b76c-5fc32f6e83c6.jpg

    (Whoever at Agie EDM designed the CPU to have a CMOS battery like this should be dope slapped rather vigiousrly)

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    That is pretty much the epitome of 'contains no user serviceable parts', isn't it?

    Good luck.

    Sent from my LYA-L09 using Tapatalk

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    Peel the plastic top off. There’s a coin battery under it I believe.

    Google Dallas box timer or real time clock.


    Sent from my iPhone using Tapatalk

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    http://www.retrotechnology.com/herbs_stuff/dallas_1.jpg

    There’s plenty of hack a day articles out there about repairing this without desoldering.


    Sent from my iPhone using Tapatalk

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    With good equipment it shouldn't be a problem if you are the first one changing it, but if you don't mind cosmetics there may be another way.

    First you need to find a data sheet because that is more than just a battery. It is also the Real Time Clock for the system. If the datasheet shows separate pins for the battery output(as opposed to IC power inputs) you can snip the leads near the IC body and solder a coin cell battery to the PCB pads. Doing it without clipping the leads might work but I'd be afraid the weak battery might drain the new one.

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    i would cut the battery/clock chip off the board, then desolder the pins individually.

    The big problem with this is not lifting the traces from overheating the board.

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    Quote Originally Posted by Scottl View Post
    With good equipment it shouldn't be a problem if you are the first one changing it, but if you don't mind cosmetics there may be another way.

    First you need to find a data sheet because that is more than just a battery. It is also the Real Time Clock for the system. If the datasheet shows separate pins for the battery output(as opposed to IC power inputs) you can snip the leads near the IC body and solder a coin cell battery to the PCB pads. Doing it without clipping the leads might work but I'd be afraid the weak battery might drain the new one.
    Edit: Here's a link.

    M48T86PC1 pdf, M48T86PC1 description, M48T86PC1 datasheets, M48T86PC1 view ::: ALLDATASHEET :::

    The datasheet indicates the battery is a separate item called a "CAPHAT". I will look into data for that.

    Correction: The CAPHAT is integral to the DIP IC, whereas the SNAPHAT is a separate item for the (surface mount) SOIC only.

    A "hack" is the only solution as even if you found a NOS piece the battery would be dead by now.

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    Here's a hackaday link to a workaround.

    A New Battery For A Potted Clock Module | Hackaday

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    There seem to be quite a few of these devices for sale so you might want to try the mod on one from ebay or elsewhere before touching the one you have. I would unsolder the IC and solder in a machined contact socket rather than solder a replacement directly. I think all your setup parameters get lost if the device powers down.

    Here is an older thread that discusses this.

    Bridgeport Cmos battery

    And another one that mentions the chip may already be socketed (post # 12). I took a closer look at your photo and the pins are round, which is uncommon with ICs that usually have flat pins although there are exceptions.

    Bridgeport EZ Trac problems

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    Quote Originally Posted by Scottl View Post

    Bridgeport Cmos battery

    And another one that mentions the chip may already be socketed
    Ironically there are many IC’s on the Agie boards that are in sockets but naturally this isn’t one of them

    FWIW, pins are not round

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    Quote Originally Posted by Milacron View Post
    Ironically there are many IC’s on the Agie boards that are in sockets but naturally this isn’t one of them

    FWIW, pins are not round
    Too bad, they looked round in the photo.

    However, the IC may still be socketed. Most normal IC sockets have flat stamped pins that are square or rectangular.

    Before desoldering I would probe with a small right angle pick to see if there is a seam where an IC plugs into a socket. It would be roughly .150 to .200 above the PCB surface.

    I'm assuming you are proficient at desoldering but just in case don't take offense at a few hints. With vacuum desoldering equipment the trick is to pace the hollow tip over the lead, wait until you feel the solder fully melt, and then lay on the vacuum while moving the tip in a tight circle to make sure all sides are clear. After all are done test each one with a pick and if one doesn't move it is stuck. Best case then is usually to resolder and immediately hit it with the vacuum desoldering unit. I've unsoldered literally thousands of connections and never lost a trace on a quality PCB.

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    5v supply are Vcc and Vss (pin 24 and 12). I measure 0 v there... is that because those are input rather than output ?

    Not socketed... for sure, absolute, cross my heart... Agie confirms this also.. in fact they will replace the RTC for 350 bucks... but I’m afraid of getting a 9 year old one, plus some paranoia about the board getting lost in shipping..

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    Quote Originally Posted by Milacron View Post
    5v supply are Vcc and Vss (pin 24 and 12). I measure 0 v there... is that because those are input rather than output ?

    Not socketed... for sure, absolute, cross my heart...
    I'd be tempted to try the hack for exposing the battery leads and soldering an external cell. I've looked but all the photos are for hacking the DS12887, which supposedly is a direct replacement so the battery is likely to be nearly in the same place.

    I did a quick cut and paste showing the pinouts side by side.

    rtc-pinouts.jpg

    I also found this video showing how to do this on a DS12887.

    YouTube

    And a link for a similar IC.

    Reworking the DS1287 / DS1387 RTC chip

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    Quote Originally Posted by Milacron View Post
    5v supply are Vcc and Vss (pin 24 and 12). I measure 0 v there... is that because those are input rather than output ?

    Not socketed... for sure, absolute, cross my heart... Agie confirms this also.. in fact they will replace the RTC for 350 bucks... but I’m afraid of getting a 9 year old one, plus some paranoia about the board getting lost in shipping..
    Yes, those are the power input pins for normal operation. The backup battery is only to maintain the onboard memory when powered down and the connections are inside the epoxy.

    Several vendors including Mouser have the DS12887+ for sale but as the datasheet is 04/10 I don't know how old the actual parts are are.

    I tried to find out what it would take to piggyback the ram and battery on a DS12885, which is the basic chip used to make the battery backup version. I found a guy, A hobbyist apparently, who had PCB modules made to do this but he is out of stock and hasn't yet ordered new boards.

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    Quote Originally Posted by Scottl View Post
    I'd be tempted to try the hack for exposing the battery leads and soldering an external cell. I've looked but all the photos are for hacking the DS12887, which supposedly is a direct replacement so the battery is likely to be nearly in the same place.
    Battery case will be magnetic, so a strong pencil magnet should be able to pinpoint the battery location fairly easily.

    I'd 100% try exposing the battery leads before trying to desolder...but I'm not as good at desoldering. I always end up with at least one pin that simply won't release.

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    here are some more links that night be useful. Apparently the battery leads are above pins 16 (negative) and pin 20 (positive). In the second link he went in from the top instead of the side and pried the button cell holder open.

    ---------------------------------------------------------------------------------
    RTC battery hacks

    This one is probably closest to working on a M48T86 since the DS12887A is very similar.

    "Tutorial: RTC replacement on older motherboards 8086 to 486"
    View topic - Tutorial: RTC replacement on older motherboards 8086 to 486 - BetaArchive


    This has a sketch showing where the battery leads are. (about 1/4 up from the page bottom)
    "Replacing the Motherboard Battery"
    Replacing the Motherboard Battery - Hardware Secrets


    These are a different pinout and probably only useful for general technique.

    "Repairing Real-Time Clock Battery (Dallas DS1287 / Odin OEC12C887)"
    YouTube


    "Dallas DS1287 RTC & other DS RTC Chip Repairs"
    YouTube

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    This is a through-hole device, not surface mount. I have undone these in the past using
    nothing more than fine soder-wick braid, a microscope, and a basic soldering iron.

    Removing the solder from the pads will still leave the pin stuck to the side of the through hole.
    Usually the via hole is large enough that pressing on the pin with iron will melt the solder
    joint holding the pin to the side of the hole. It will spring to the side in the hole when this
    happens. At this point remove the iron and the copper via will have enough thermal mass
    that the pin will not re-bond to the side of the hole. Then one pin is completely free.

    1) you need to do this about 24 times.

    2) you cannot do it unless you can see what is going on in there, ie good binocular microscope.

    3) if the pin is *really* tight in the via than this approach probably won't work. Most layout
    guys put enough clearance between the pin and via, for assembly purposes, that it works most
    times.

    If you get the part out of there then clean up the remaining solder in the vias before putting
    the new one in.

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    Assuming splicing in a new battery to this chip doesn't work (interesting idea), then I'm with Jim on this one. Solder sucker out what you can, wick out the rest, and don't let the pins touch the walls for a moment as the wall cools.
    I had a chip that *would not* let go of three pins once in such a way that heating one pin and shoving the chip out a little bit/swap to the next stuck pin didn't work. A soldering iron on 2 of the 3 problematic pins (extra set of hands) did allow one end to be pushed out, back to the bothersome pin at the first end, and repeat.
    Never a good start to the day when Digikey and Mouser list it out of stock, but Amazon has the part for <$10, age unknown. Wouldn't surprise me if Tanner Electronics in TX had one sitting on the shelf for $0.25, although I don't know if they ship.
    As stated, get the holes nice and clean before reassembling.

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    There is a special flux and low melting point solder that makes removing ICs like this much much easier By applying it to each pin and diluting the original solder things stay liquid far longer.

    I think that it’s intended for unsoldering SMDs but I also use it on through holes devices to good effect.

    Ebay will provide

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    Hey Don how are the cats doing ?
    I cannot added anything regarding the components +/- battery that has not already been said. BUT
    Is the board conformally coated? I ask cause this can be a fly in the ointment when de-soldering. As said those holes are through plated, so as you now gentle is way. I assume from what you said you have the vacuum de-soldering bit of kit. The one tip I can offer is when de-soldering a large IC like shown is to place a dab of heat sin compound on top. Then put an appropriate sized piece of Al on top of it, just decreases the chance of cooking the chip. I usually put a socket in so do not have to worry about too much heat going into replacement & if you need to remove it again for testing or what have you, much better. Bearing in mind that some ICs are not socketed for a reason, longer the pin to board distance the more apt it is to possibly pic up interference.
    Good luck, hope my little anecdotes, are of some help. Solder wick is great but I use to clean the holes after extraction, using it in place of a proper sucker IMHO requires too much time to heat, thus more heat into IC, it great for quick removal of most other discrete components resistors caps etc.
    Regards, Doug


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