I began restoration of another vintage motherboard, this time Socket 3 486 model.
As usual there was a sign spilled acid from VART battery. Fortunately corrosion was mild and localized. Battery was already removed by the previous owner.
Aside the main problem that I will describe in a moment, there was a "keyboard error" message appearing on the POST screen. The keyboard was in fact non functioning. There were two suspiciously looking traces near the keyboard socket/battery. I removed th socked just tu bu sure there is no more destruction underneath. Fortunately damage was minimal, even the suspicious traces turned out not to be broken. After cleaning the area, tinning some traces and soldering keyboard socket again "keyboard error" disappeared.

Unfortunately there still is another problem. Board doesn't boot properly after connecting power. It sticks at diagnostic code, usually 05 06 or 13 14. After manually shorting RST pins it boots and appears to work normally. In rare situation manual restart needed to be repeated to have an effect. What may be the cause of such behavior? In 8bit systems there usually was a simple circuit, responsible for resetting CPU some time after power up. It looks like in this case such circuit is failing to do its jobs. How to locate and diagnose the it? May it be the fault of my power supply - mainly the fact that it has switch cables permanently shorted and is powered on by the plugging cable to the power strip?

Byt the way this board turns out to be quite picky when it comes to the RAM. It works with either 4x1MB 30-pin SIMM modules or 2x4MB 72pin single sided modules. It refudes to work with double sided 8MB modules.

Additional question. I am using this board with Am486DX 40 MHz CPU. Does it require external heatsink/cooler (I do not any at this moment) or can I use it safely without it?