This is a 386sx Packard Bell motherboard with no battery leakage or corrosion. It has a Phoenix bios, 2MB RAM onboard, Oak VGA chipset onboard.

Symptoms:
* Himem.sys freezes system or causes reboot loop. (this happens even before the testing ram message appears) DOS boots fine without himem.sys.
* Once in reboot loop, POST card bounces between codes and reset signal rapidly fires. (See video)
* The longer the motherboard is powered on, the more the VGA signal from the onboard Oak VGA chipset becomes unstable. The visible noise in the picture varies with system activity. Seems to be related to ISA bus activity?

What I've tried:
* New known good power supply -- No change
* Tried a discrete ISA graphics card -- No change
* Ran 5 passes of Memtest86+ 2.11 -- No failures

Other observations:
* Nothing on board ever gets hot to the touch
* No excessive ripple is seen on +5V or +12V motherboard rails using oscilloscope
* Board has no battery damage or corrosion. It's pristine.

POST card freaking out after himem.sys causes reset loop. Notice the rapid firing of the reset led.
https://1drv.ms/v/s!Aq_S4PNq1opGgptkWrR5wUpsdzpQmw?e=ahOvGF

Demo of the VGA noise that appears after machine has been on for a while
https://1drv.ms/v/s!Aq_S4PNq1opGgptjeUk9OZsPYfTs6A?e=Q9NJCp