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Toshiba 3100e/40 BIOS won't save settings with new battery

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First post, by geiger9

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Hey all. So when I bought this machine, the lithium 4.6v battery was dead obviously so my first instinct was to replace it with a CR2032. When I went to disassemble the machine, I noticed that there was a diode installed on the positive lead of the battery wiring. When I wired up a CR2032 battery holder, I kept the diode. With a fresh battery I tried saving the BIOS settings but they weren't sticking. Then I thought about the voltage. The initial battery was 4.6 with a diode so there would be voltage drop. I tried removing the diode from the battery holder. Now with 3V I tried saving the BIOS settings again. No, still not saving. Next, I tried wiring up 3 AA batteries for a total of 4.5v. I tried it with the diode installed. Not saving settings.

The only other clue here is that when I connected the 3 AA batteries, sometimes the positive pin on the header on the mobo would be tied to ground and other times it wouldn't? It was only when the connector was plugged into the header. Something tells me I've made a mistake. Go easy on me. hehe.

Reply 1 of 1, by geiger9

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I learned something in my few days of trying things.

I can't access the BIOS on this machine using a key or key combo unless I remove the CMOS battery. When I do this and power on the machine, it will complain about an error in CMOS and allow me to press F1. Otherwise no key combo will work. I have tried esc, F1, del, F10, and then combos with the ctrl, alt, shift, and fn keys. The only way I can access the BIOS settings (it appears) is if I get to a DOS prompt and run Toshiba's test3.exe program to access it. I did a test where I entered the date/time after DOS booted. Then I powered off the machine and then back on and checked the time and date. It was retained. Next I ran the test3 program and exited the diagnostic menu. The date and time were retained. I ran test3 again and entered the BIOS. I made no changes, didn't save, and exited. The machine reboots. I check the time and date and it has been reset.

The RTC/CMOS chip is a Motorola MC146818. I'm not the greatest at understanding datasheets but if you look on the last page, there is the pinout. I don't know what terms like Vss and Vdd mean. I check Vss when the computer is off and it's 4.1v. If I check Vdd it's 0.

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