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ASUS ISA-386U3Q - irregular counting of seconds, clock stops shortly after powering off

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First post, by maciejd

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Hello. The saga of ASUS ISA-386U3Q does not keep BIOS settings for longer time (several+ hours) continues and I think I'm close to give up.

The situation:
- when powered on, the seconds are very irregular every 3-2 seconds: https://youtu.be/L-6Oz9V_OHA
- after powering on, the date is kept, but clock seems to stop , for first seconds behaves like this: https://youtube.com/shorts/2B2IwLB-_Rg?feature=share

I guess it might be the 32.768k KDS30... Can I replace this with any 32.768? Ir maybe the problem is somewhere else? Irregular counting points to the crystal. Not keeping/measuring time when on battery (it's new)/powered off points to the crystal and/or power.

Does anyone have any suggestions? I really like this motherboard and it would be a pity to let it just die.

Reply 1 of 4, by rasz_pl

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yes crystal, but i also see some green on the legs nearby suggesting battery leaked? that might mean some corroded tracks and vias

https://github.com/raszpl/sigrok-disk FM/MFM/RLL decoder
https://github.com/raszpl/FIC-486-GAC-2-Cache-Module (AT&T Globalyst)
https://github.com/raszpl/386RC-16 ram board
https://github.com/raszpl/Zenith_ZBIOS Zenith Z-386 MFM-300 ZBIOS disassembly

Reply 2 of 4, by maciejd

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rasz_pl wrote on 2026-06-12, 06:47:

yes crystal, but i also see some green on the legs nearby suggesting battery leaked? that might mean some corroded tracks and vias

Rather dust, the battery started leaking slightly, but has been replaced. I cleaned everything with vinegar and IPA. Tracks are fine, only slight surface corrosion appeared nearby the battery, cleaned out, checked paths, were ok.

I'll try to buy the crystal today and will see. Also a good reason to buy a soldering station 😉

Reply 3 of 4, by rasz_pl

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Green is not dust, its corrosion. You dont have to leak liquid directly on a track/via to corrode it, mere vapors are enough, especially for VIAs as copper is very thin (electroplated) there.

https://github.com/raszpl/sigrok-disk FM/MFM/RLL decoder
https://github.com/raszpl/FIC-486-GAC-2-Cache-Module (AT&T Globalyst)
https://github.com/raszpl/386RC-16 ram board
https://github.com/raszpl/Zenith_ZBIOS Zenith Z-386 MFM-300 ZBIOS disassembly

Reply 4 of 4, by majestyk

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The effects of the battery leaking are more severe than you might think, I´m afraid.
Look at the ISA slot - the leakage has even reached / creeped up the contacts inside the ISA slot (blueish discoloration).
Same goes for the solderings at the clock gnerator´s quad-inverter - all blueish and rough on the surface.
--> replace the crystal, desolder (and replace) the 4069, check and clean (re-tin) all the traces underneath the chip.

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