I have the same mobo, thanks for the tip 😀
but you are using it with a BIOS from a different mobo? that's not such a good idea IMHO

No i just HOTFLASHED the BIOS, in a different motherboard. Then seated the
FlashROM chip. I just wanted to point out, that you can use modern 256kb FlashROM chips in a 128kb 386/486 motherboards, and even replace EEPROM chips.

🤣 OK , I did not understand it well 😀 thanks for the tips!

I have the same board(no red glass diodes, though). Right now the battery looks to be in perfect condition, but I was wondering if there was any reason to replace it with a lithium battery pre-emptively? Any harm is just waiting for it to die someday?

Cyberdyne wrote:

Near the battery, there are 3 red glass diodes, if you remove the middle diode, you can replace the old bad battery, with a lithium cell socket, and put a new battery in, and you have a working system.

Could you add a picture of your board, please? I think there were at least two versions of it.

I have one of it, but didn't have to remove any diod to solder the new battery socket on it.
However, as the old NiMh battery is rechargeable, my fear is that the current is to high even for a rechargeable lithium cell. So did you remove the diod because of this or because it was in the way?

This diode is conected to +5V line and other end is thru a resistor near the battery.
This will provide charging current to the battery. Then you can modernise your mobo. Because today every board uses lihthium cells.

I am resurrecting this thread because I got back my SY-4SAW2 system and upon checking I found the dreaded V11H battery was starting to leak... fortunately it was in the beginning and no serious damage was done... here are 2 pics with the barrel battery removed:

Cyberdyne, is it really safe to remove the center diode and place a coin CR2032? I don't want to blow the mobo 🤣

Yep middle diode has to be removed, so the lithium cell does not get charged.

ah thanks for verifying this, I will solder a battery holder and fix this... I am unsure if I need to repair the affected tracks, do you think I should scratch them a little and put some solder on them making a patch ?

keropi wrote:

I am unsure if I need to repair the affected tracks, do you think I should scratch them a little and put some solder on them making a patch ?

From the photo, it looks to me as if the acid just ate away at the protective coating on the two traces. Check the resistance of the two trace ends with a multi-meter to ensure continuity.

There is no harm in gently scratching away at the remaining traces with sharp edge to expose the copper. After doing this, you can re-verify continuity with a multi-meter directly on the traces. The only problem with a continuity-only test is that you don't know how thin the trace has become (and thereby how much current/heat it can take), but in this case, such a small amount of current is being sent anyway, so I don't think it will matter. Just ensure that the BIOS holds charge.

I personally wouldn't ugly up the board with solder. If you scratch off the trace layer to expose the copper, be sure to cover it afterwards. For my last acid leak job, I used clear boxing tape to cover the traces and everything has been working fine for some time. I just replaced the rechargable battery with another one since I had extras.

Cyberdyne wrote:

Yep middle diode has to be removed, so the lithium cell does not get charged.

It sounds like your purpose in removing the diode is to break the electrical path to the 5V source for charging the battery. If you didn't want to remove the diode, you could cut a chunk out of one of the leads to break the connection.

Yep, I just examined the board in daylight, it's just the coating that got discolored.... will remove it from the case an clean it up better tomorrow at my office and decide what to do with it. Luckily none of the nearby components or thiner tracks got affected 😀
The board also has pins for external battery and I got a couple of those lying around unused, will check them and maybe use one of those packs instead of a coin battery holder... though a holder will also cover up the discoloration.... 🤣 it's nice to have options 🤣

just a small update, coin battery holder installed, D2 removed and everything working perfect 😀 thanks a mil or the info Cyberdyne !

Don't want to necrobump (if that's possible in a forum about old stuff), but:
I removed the middle diode and soldered on a coin cell holder.
Works, but:
The coin cell only lasts a few weeks. After 1-2 months they're empty.

Curios how often you turn the board on and for how long ? Most CMOS quit saving when the volts drop below about 2.8-2.9 volts.
The original battery looks like a 3.6V barrel, the new coin cell are 3v but are about 3.1 to 3.2v when new.
A CR2032 is rated at about 220mAH (and nominal .2mA discharge) so with a 15kohm load will only last about 1000 hours/40days according to Maxell CR-2032 load vs time charts.
Your board CMOS probably draws only about .05mA but because the battery already is starting at a -.4v deficit compared to the original 3.6v it dies more quickly than a different board designed and already includes the coin cell holder.
BTW the CR2016 coins are only 1/3 the capacity of a CR2032.

Lithium cells are more voltage stabile and the end dropout is fast. I used a CR2032 cell. And they last few years, but I only use used scavanged cells from more modern motherboards. In my line of work i sometimes have access to loads of scrapped P4 motherboards and other stuff. I have always minimized the things I have to buy for my hobby.

Cyberdyne wrote on 2021-01-07, 07:03:

Lithium cells are more voltage stabile and the end dropout is fast. I used a CR2032 cell. And they last few years, but I only use used scavanged cells from more modern motherboards. In my line of work i sometimes have access to loads of scrapped P4 motherboards and other stuff. I have always minimized the things I have to buy for my hobby.

I would be interested in buying some of them, and, what "other stuff"? let me know, no hard feelings if you don't want to bother with this.

Dusko dude I live in Europe, and you in USA. The shipping fees will be a bitch. It is better to look at local craigslist or something. I have some very exotic stuff even original Voodoos and Gravis Ultrasounds and 486 stuff that I plan to sell, but definitely not in Ebay, and a have not get into Amibay yet. well even in Estonia one crazy guy just bought a 5.25 1.2MB floppy drive from me, but our retro computer fanbase is small, and usually not with deep pockets. And I am not hurting for money, but I have hoard so much that I really do need to sell something.

I recently gave it a try and used a supercap (1.5F, 5.5V) for replacement.

I left the charging circuit unchanged. The charging takes about 1 hour and it´s enough to store the settings for about 2 weeks.

If it´s an active system that´s in use frequently this would be an elegant solution. You could even use a 3µF supercap (same diameter, double hight) for a longer duration.
There´s no need to replace any coincell again and leakage is not to be expected.
It wont´t be a solution if you intend to store away the mainboard for ages and need it to keep all settings.

The problem I have with supercaps is that even if the settings are stored properly, the time is getting off very quickly 🙁