I have one, think it a rev 3, (all rev's are near identical except for the 3.3v regulator portion). Without that JP8 there is no way to use the onboard battery (pins 2-3 closed) OR connect an external battery (pins 1 and 4).
Mine also had a keyboard issue (was the data line), some corrosion at some via's caused it due to a leaky battery. As long as the KB leds flash when first powered up then it is getting the +5v so could be the data or clock signal.
I cannot remember all the details of keyboard to chipset (UMC UM 8496) but do remember the kb data line went to it's pin 30, cannot remember which pin is the kb clock line. In the picture below I charted where the KB signals go,
use continuity and check each point with one lead in AT connector pin 1 and and then pin 2 and do same. Some where lost have notes on what I found, not sure where the motherboard is or could retrace the clock line #1 better for you...

edit: I labeled the AT KB socket wrong, sorry !

I'm guessing it's probably corrosion underneath the clock chip given that there are no other visible signs of corrosion on the traces. I appreciate the picture, I tested the traces I could find (no issues with those) but wasn't sure about which ones come from below the clock chip. Perhaps the pressure change from plane ride it went on caused the battery to finally spill its guts on the board underneath 😒

The keyboard does get +5v since it flashes, and it does cause a beep when I press keys during the POST screen, but it doesn't read any further inputs. I was planning to desolder the clock and replace it with a modern substitute anyway so I guess I'll find out for sure when I pop that off.

In retrospect I'm wishing I'd gone with a MB that has the old fashioned barrel battery, at least those are easy to diagnose and replace. Being a complete noob at 486 era PCs I didn't realize these stupid unserviceable clock units were a thing.

Also looking further in to it, I think mine is a rev 6? it's strange that it's missing the CMOS jumper since that seems to be the one thing that doesn't line up with the documentation.

I'm probably going to test that hole drilling/coin battery fix for the clock and if that doesn't make any difference I'm going to say screw it and stick the 386 back in to play some Wing Commander while I wait on a replacement.

I'll go test those traces now and see what happens.

Oop, forgot to include the images I just took. I'll admit I'm a little surprised that I'm having these sorts of issues given how clean this looks otherwise.

Update: the fault is somewhere between pin 1 on the AT connector and the barrel thing at L3 (I'm not an electrical engineer, its the grey cylindrical thingy next to the ISA slot). Pin 2 is showing no faults and is clear all the way to the chipset.

Ahh you have the Odin 12c887a RTC, for that JP32 is the cmos clear (jump for a few seconds then return to open) not JP8. Yes do the battery mod on it to get rid of the low battery part.
Mine looks like this: https://theretroweb.com/motherboards/s/biosta … -1433uiv-ver.-5 the manual applies to nearly all the versions...
L3 is an inductor in line with kb clock to chipset. Good luck !

Where´s L3 located? I cannot find it on my 50UIV.

L3 and L4 located between 3rd and 4th ISA slots from ram, next to the cpu jumper/speed silkscreen on a picture of mine (ver 3?) and in the picture above (think it a ver 6?) I attached.
EDIT: sorry I labeled #1 on the kb connector wrong in the picture, had it pointing to #3. FIXED. sorry !
Added: I vaguely remember that clock line went to the big chip at about pin 165 or there abouts, on that side anyway....

Horun wrote on 2025-03-21, 14:21:

Ahh you have the Odin 12c887a RTC, for that JP32 is the cmos clear (jump for a few seconds then return to open) not JP8. Yes do the battery mod on it to get rid of the low battery part.
Mine looks like this: https://theretroweb.com/motherboards/s/biosta … -1433uiv-ver.-5 the manual applies to nearly all the versions...
L3 is an inductor in line with kb clock to chipset. Good luck !

Thank you for this! Knowing where that is will definitely be useful info.

Unfortunately I botched the chip mod so I need to find a replacement (Cut too deep with the Dremel and broke the pin off too low to solder, I got ambitious and tried to sever the negative for the original battery.) I'll take advantage of the opportunity to install a socket so that I'll never have to suffer again if I have a need to replace it in the future.