Battery replacement on GA-486VM \ VOGONS

Battery replacement on GA-486VM

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First post, by Sedrosken

Posted on 2020-05-25, 09:08

Sedrosken Offline

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Hi,

I've got a GA-486VM coming, and I know it's got one of those evil barrel batteries, thankfully it hasn't leaked yet. I hear that you can, upon removing said evil battery, solder on a CR2032 holder with an appropriate diode drop (I believe to bring the charge voltage in line), and I was wondering about the specifics of that? What value diode would I use, and what's the procedure for doing so? Please bear in mind I'm a soldering novice at best.

Failing that, does it have an external battery header, and would it just be easier to use that? Does this header also try to send a recharge signal, or can I cheat and try for some combination of AA or AAA cells?

Also, if anyone happens to have a copy of the manual, can you point me to it? Cursory Googling doesn't really reveal much other than a stason.org listing of the jumper blocks which while better than nothing doesn't particularly fill me with confidence.

Semi-offtopic, as well: what are my upgrade options? I'm pretty sure I have just the basic 168-pin non-ZIF socket so I know the Pentium Overdrives are out, not that I'd want one of those anyway. Is the board considered stable at a 40MHz FSB, and would I need to swap a crystal to run that? Does the voltage regulation properly handle 3.3v CPUs? Can it handle a Cyrix Cx5x86? Would I need a specially packaged one with voltage regulation and clock multiplier overriding, since I'm pretty sure it only properly supports up to a 2x multiplier? It currently has a DX2-66 and I feel like with the 32MB of RAM it's got, 256K L2, and a decent VLB video card (I've got the TGUI-9440 1MB in hand for it) it should just about handle Diablo 1 under Windows 95 with the music turned off, and that's by far the most stressful thing I plan to run on it -- everything else will either be much less intensive, or just run under DOS anyway.

Last edited by Sedrosken on 2020-05-25, 10:03. Edited 2 times in total.

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Reply 1 of 4, by Doornkaat

Posted on 2020-05-25, 09:50

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The diode is used to prevent the motherboard from loading the CR2032 when powered up.

The motherboard has an external battery connector (J2) right next to the upper 8bit ISA slot. This external header usually features a diode that'll prevent the attached battery from being loaded. If you have little electrical knowledge this header is your safest bet. One of the outer pins is ground the other outer pin is positive. Use a multimeter to figure out ground and attach a battery accordingly. While doing so you can also make sure the header does not get power when running the motherboard.
Usually the battery will be either ~3.5V or ~4.5V so I suggest starting with a CR2032 holder and if that doesn't do the trick go for three 1.5V cells in series.

Good luck! 😀

Reply 2 of 4, by Sedrosken

Posted on 2020-05-25, 10:01

Sedrosken Offline

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Doornkaat wrote on 2020-05-25, 09:50:
The diode is used to prevent the motherboard from loading the CR2032 when powered up. […]
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The diode is used to prevent the motherboard from loading the CR2032 when powered up.

The motherboard has an external battery connector (J2) right next to the upper 8bit ISA slot. This external header usually features a diode that'll prevent the attached battery from being loaded. If you have little electrical knowledge this header is your safest bet. One of the outer pins is ground the other outer pin is positive. Use a multimeter to figure out ground and attach a battery accordingly. While doing so you can also make sure the header does not get power when running the motherboard.
Usually the battery will be either ~3.5V or ~4.5V so I suggest starting with a CR2032 holder and if that doesn't do the trick go for three 1.5V cells in series.

Good luck! 😀

Thanks very much for the information! That's probably what I'll end up doing then, just for simplicity's sake.

Reply 3 of 4, by Doornkaat

Posted on 2020-05-25, 10:08

Doornkaat Offline

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Happy to help!
Let us know how it turns out. 😀

Reply 4 of 4, by Sedrosken

Posted on 2020-06-10, 15:13

Sedrosken Offline

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I've discovered that with power on, there's no power at those pins. I tried a CR2032 for giggles and it holds the data and runs the RTC, but it *should* be fine with a AA battery holder.

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