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486DX2 motherboard... where's the CMOS battery?

I take the battery holder, put a piece of double-stick foam tape on the back and slap it on the side of the power supply. Works great. If you're paranoid, you could put it in a plastic bag and hang it outside of the case.
 
Chuck(G) said:
I take the battery holder, put a piece of double-stick foam tape on the back and slap it on the side of the power supply. Works great. If you're paranoid, you could put it in a plastic bag and hang it outside of the case.
Click to expand...

I just realized that the OP said "can't find a place". Perhaps he didn't catch the idea that those battery holders have wires and you can make them as long as you like. Indeed I've usually just dangled those holders outside on the back, for no particular reason than that it's easy and convenient.
 
Sigh. So I got a 6v battery and a battery holder. First I tried soldering it to the battery area. I double checked with my multimeter that it's getting 6v. Still says the CMOS battery is low, won't save CMOS settings. So then I soldered the holder to where the manual says to connect the external battery, and same thing. Still says CMOS battery low and won't save settings. I checked this one too with my multimeter, and it's getting 6v.

Any other ideas?
 
I didn't think you could use an external battery with an RTC chip containing its own battery, at least not without some mods...
 
MikeS said:
I didn't think you could use an external battery with an RTC chip containing its own battery, at least not without some mods...
Click to expand...

My 386 arrived with an RTC + battery combo, and an external coin battery hooked up. For some reason I unhooked it and haven't put it back. Seems to remember the CMOS settings but can forget the time after a week or two. Was definately designed to have both, not sure if there is some trickery to prevent the good battery from wasting energy on the old one or not.

I usually use covered AA battery holders that clip/screw together. Eliminates any chance of shorting or leaking, but the coin + double sided tape idea is perfectly good (I guess I was just being a bit picky because the first two I did were going in to portables and I had cheap double sided tape).
 
See Photo 2 you posted:

Notice where u put the red circles. There is a screw hole, just to the left is a visible trace that ends. Notice how it leads to the jumpers. Solder one side of the battery to that, not sure on the polarity without being able to see which one leads to the ground. Guessing thats the positive lead, and the ground is shared with the keyboard port.
 
Ole Juul said:
I just realized that the OP said "can't find a place". Perhaps he didn't catch the idea that those battery holders have wires and you can make them as long as you like. Indeed I've usually just dangled those holders outside on the back, for no particular reason than that it's easy and convenient.
Click to expand...

To put an image to it:

IMG_3127.JPG


IMG_3127_bis.JPG
 
If you still can't get it to work by soldering the battery/wires to the alternate battery leads on the board, then you could solder them straight to the chip if it is a 12887 clone.

I used this guide here for the pinout: http://www.hardwaresecrets.com/article/Replacing-the-Motherboard-Battery/81/3

The RTC chip on my 486 board didn't have legs for pins 20 and 16, so I tore/cut open the outer plastic shell of the RTC and found the leads for them. They were exposed enough to solder the wires to them for my battery pack, and so far it's been working great.
 
Well, this is turning into more trouble for me than it's worth, especially with my limited knowledge. I don't want to fry the computer like I did with my IIgs. :(

If anyone is interested in buying it maybe they'll have better luck at modifying the battery. I think I'll just look for a 486 motherboard with a normal battery. I'll post in the other thread.

Thanks for all the help, but I'm just worried if I make any more changes I'm going to irreparably damage it somehow. I'm pretty jinxed when it comes to that. :/
 
Could even put a socket in for easy replacement in future. May be a clearlence issue for the isa cards though. Nothing a demel can't fix...............
 
Well, that's the fast and dangerous way to do it. But if you're worried about damaging something, you could go a little safer with an Exacto knife.

Can you give us a picture of what you're working with here?
 
Just take a sanding / plastic bit , pop it on your dremel, and use it to expose the battery pins, solder your new battery holder to that... Like SeGamer said...
 
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