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POST hang on 486 after barrel battery removal

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First post, by marvias

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Hello, I decided that it is time to remove the barrel battery from my 486. So after de-soldering, I connected battery pack to EXT battery connector. But now, regardless if its connected or not, system hangs after checking memory and printing WAIT... to screen. Num lock on keyboard then blinks once and speaker gives one continual beep until I turn computer off or hit ctrl+alt+del.

on the image with battery still connected, there was jumper between pin 1 and 2 of ext_battery connector. + side of barrel battery is connected to pin 2, and - side to pin 4. After removing barrel battery, I removed jumper, connected external pack + to pin 1 and - to pin 4. Is that correct, or should + be connected to both 1 and 2? or only 2?

When I put barrell battery and jumper back, it still hangs on POST, although it measures only 2V now. And I didn't try to start computer before removing the battery, last time it ran fine several months ago 🙁 I tried to replace CPU and reseat memory, also remove all cards except VGA, but issue still remains.

Any advice is welcome.

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Reply 2 of 6, by marvias

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Its this motherboard
http://arvutimuuseum.ee/th99/m/U-Z/32207.htm

I just realized that I even found manual for this thing, so here is battery connector description. Should external battery be connected to pins 1 and 3?

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Reply 4 of 6, by quicknick

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If you can enter BIOS setup, try booting with external cache disabled. On two of my boards with similar AMI BIOS, hanging at WAIT... was caused by ext. cache problems.

Also, for testing with the original battery, I think 2V is not enough. Charge it, leave the board powered for a few hours if you don't have other means.

Last edited by quicknick on 2018-11-11, 09:12. Edited 1 time in total.

Reply 6 of 6, by marvias

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Looks like that I was just impatient.
I originally waited just about 10-15 secs because of that terrible speaker sound. Today I charged the barrell battery, it took only 4mAh and voltage went up to 4.6V. I disconnected speaker, started pc and waited. After about 30 secs or so, I got error saying CMOS options not set. And was able to get to bios after clicking F1.

Could external battery pack have too high voltage? I used 3x Energizer ultimate lithium AAA, but later measured that they are over 1.8V, not 1.5 as advertised and thus 3 have 5.5V. It seems to work OK now when using 2. Just cdrom connected via soundcard ESS 8168F now gives 2long beeps and 8 short after start and the whole system just hangs without even displaying anything, while before it worked fine. have to investigate that.

Thanks everyone for help.

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