Hi there, fellow 486DLC owner! 😀
That's a nice box you have. Looks clean and shiny. And gratulations on the CT1740, it's a fine card.
Albeit a bit noisy for some (hence sometimes called Noise Blaster).
Anyway, it makes up to that by being a stress-free and quite compatible card with a real OPL3.
If you want to increase audio quality a bit, just by-pass the amplifiers.

About that battery thing.. Your system had a 3.6v battery, right ?

In this case, here a two ways to use 1.5v batteries:

a) 2x AA and a germanium diode (voltage drop ~0.3v)
b) 3x AA and a silicon diode (voltage drop ~0.7v)

Of course that's just an example here. The internal clock requires very little current,
like a watch, so any battery will do. Including triple A's.

You could also use an old-school 4.5v lamp battery (3LR12) with a silicon diode.
Or a coin cell with a germanium diode. Or a tiny rechargeable battery (NiCD).

Just keep in mind that batteries without a load have a slightly higher voltage than said.
And the clock+CMOS make up for a very lousy load, comparable to a solar powered calculator.
So if you want to stay on the safe side, use a lower voltage (you can also use diodes in series to do so).

Very nice PC that you got there.
I believe the motherboard is a Dataexpert EXP3406 - http://arvutimuuseum.ee/th99/m/C-D/31975.htm
I have the same motherboard. The only difference is that mine has the OPTI 495XLC chipset.

Regarding battery replacement, refer this site for some tips - http://pc-restorer.com/replacing-cmos-batteries-in-old-pcs/
For older motherboards, I prefer an external battery connection.
I've used a 4x 1.5V battery "pack" on most of my 386 & 486 motherboards with no problems (non rechargeable).

Just remember, when you do put the motherboard back together, the two black wires from the power supply goes together when you plug them onto the motherboard.

PS: When you do get the motherboard up and running, I would like if you could dump a copy of your motherboard's BIOS for me (I'm looking for an updated revision for mine).
You can use a utility like NSSI 0.60 to save a copy of the BIOS.

Why add a germanium diode to 2xAA batteries? The 2 batteries in series will give 3V, minus the 0.3V (actually most germanium diodes are 0.4-0.5V drop) would give 2.7V or less.

stamasd wrote:

Why add a germanium diode to 2xAA batteries? The 2 batteries in series will give 3V, minus the 0.3V (actually most germanium diodes are 0.4-0.5V drop) would give 2.7V or less.

The diodes do also act as some kind of "flow control" - they let pass the power in only one direction.
It is used as a safety measure here, to avoid the batteries beeing charged.

Besides, if you cascade two 1.5v batteries, you won't get precisely 3v, but something like 3.2v.
That's similar to lab power supplies. They aren't rated 12v, but 13.8v.

You don't have to worry about the batteries being charged via the external battery connector.
It only draws power, there is no charging occurring via the external connector.
Unless, I completely misunderstood your post.

You're right, I thought the OP was asking for a way to replace the on-board battery.
Using an external battery on the connector is safe, as you said. 😀

Jo22 wrote:

You're right, I thought the OP was asking for a way to replace the on-board battery.
Using an external battery on the connector is safe, as you said. 😀

It just occurred to me that there are some motherboards that do charge via the external battery connector (I have an AMD 386SX-25 motherboard that has two external connectors - one for chargeable batteries and the other one for non chargeable batteries).

Always best to check the jumper settings of the motherboard as well.
However, if the motherboard already had an onboard (soldered) battery, then chances are good that the external connector is only for non chargeable batteries.

Wow thanks for all the info everyone! I finally have the model of the motherboard. I looked all over for that. I'll try to dump the bios if it gets up and working. As for the batteries I found one of those cordless phone battery packs in my basement. I think I might just wire that in and tape it to the side of the case. I don't understand why people use alkaline or lithium batteries with a diode. Why not just use a lithium-ion coin battery like this soldered onto the motherboard in a holder?

Glad we could help! 😄 I don't know if this works, though. There are two types of lithium coin cells.
Batteries (primary cells) and rechargeable batteries (accus). As a direct replacement (no diodes) you could use
NiCD and NiMH types, but I think lithium models need a different charging technology.
That's at least what Jesolo's wonderful link hints (see "Do’s & Don’ts" paragraph).

Just want to add to Jo22's last post.

Just be very careful in connecting a non chargeable battery (like a CR2032 coin cell) to the connector on the motherboard where the onboard (rechargeable) battery used to be.

On my other AMD386SX-25 motherboard I made the mistake of connecting my "battery pack" to the connector that is the chargeable one, resulting in my AA batteries heating up very quickly. Luckily, I caught it on time.

Well the parts came in. I soldered in a battery pack (NiCad) and a keyboard port. However with only the video card connected I don't get any posts or beeps. With it disconnected I get 2 beeps followed by 8 beeps. I'm pretty sure 8 beeps just means no VGA card. Did the video card bite the dust or something?

Are the ISA slots pkay ? Sometimes a pin gets bent, and shorts another one..

I didn't see any bent pins but you gave me an idea that it might be something with the ports so I used electronic cleaner and a credit card to clean and loosen the ISA pins and now it boots!

Edit - So after all that work I'm back to my original problem when I first got the computer. I don't have a hard drive hooked up. I just have the video card, I/O card, and gotek FDD emulator. I try to boot from the floppy which has the DOS installation disks and a DOS bootdisk. I can see the green light come on and then the usb stick has an indicator light which starts flashing when its reading. Then either I get stuck at "Wait..." or it acts like its launching whatever is on the floppy but the monitor goes black. Actually it looks like it is out of sync its doing this wavy black picture. I tried using another monitor but it just says no signal when this happens. I was stuck at this before and I don't have any better idea now what could be causing this.

jesolo wrote:

I have the same motherboard. The only difference is that mine has the OPTI 495XLC chipset.

Maybe the layout is the same, but otherwise not the same at all.

jesolo wrote:

You don't have to worry about the batteries being charged via the external battery connector.
It only draws power, there is no charging occurring via the external connector.
Unless, I completely misunderstood your post.

Uhm...nope. Some motherboards provide a 5v charge current trough the external battery connector. Look here:

My 286 board does not provide any charge current, but my two 386 boards and most of my 486 boards provide 4 to 5v trough pins 1 and 4. Using non-rechargeable batteries on these w/o clipping D2 on the motherboard or installing a diode on the battery pack could be dangerous. I found that out the hard way.

I am truly stuck. I only have the video card, Biostar I/O card, and FDD hooked up. I've tried swapping out IDE cables, flipping the IDE cable around, changing out floppy disk drives, pulling the I/O card and checking the jumpers and re-seating the card. Every time I boot up I get past posting with 1 beep, the FDD is being read and either the screen goes black, the computer just sits at the wait screen, or the screen gets all wavy/blurry at the wait screen and just sits there all the same.

I found other threads both here and elsewhere with people hanging at the wait screen and none of them were resolved. The bios shouldn't need to be reset as that would have been done when I replaced the battery. I can only think that either the video card or the I/O card is bad. It seems weird for the video card to be the culprit as the issue appears AFTER posting. I would think if it were the I/O card it would say bad FDD controller at startup. Unfortunately this is the only ISA/VLB hardware I have at the moment.

Can you access the BIOS and disable the L2 or external cache option? See if it boots now.

With the ribbon cables, to avoid guessing, one outmost cable is red (on the ribbon cables), that one goes to pin 1 on the controller and drives. That just gives you something to check for and to know it's 100% correct.

Thanks for the suggestion. I gave it a shot disabling a combination of external, internal, both, and also the turbo button. I think its random what occurs but I was able to get the farthest yet with the computer locking up midway while drawing the system configuration screen. Weirdly disabling both internal and external led to the computer just doing 1 long beep but it has done that before randomly.

This is the Wait.... screen. It either shows up wavy like this or clear and just sits there

After messing with the caches I got this:

And then this:

All of the above seems random. I can't tell if I just got lucky or if disabling the caches made me get further as each time I try something I get one of the above results.

It seems like a problem with the DMA controller. Make sure your bios settings are correct. Try "load optimized bios defaults" or something like that. If it still won't work, try decreasing DMA clock in bios . if it's 1/1 or 1/2, set it to 1/3, 1/4 or lower. Try this with all bios multipliers if defaults don't help.

Also, are you using a VLB video card or I/O card? Is the TVGA 9200CXr VLB? If so, VLB might be running too fast - see if the board has a CPU Clock > 33Mhz jumper or bios setting - if it does, you might have to set it on. This dictates the frequency of the VLB bus. At CPU < 33, VLB will run at CPU clock witch in your case is 40MHz. Some VLB boards don't like going over 33Mhz, so set the jumper to CPU > 33Mhz witch wil half the VLB frequency.