Hi there,
I had similar problems with my HOT-409 - different revision - recently.
The traces around the battery had been corroded and undermined, one ISA slot had corroded contacts and a second ISA slot had broken contacts.
After removing the battery I cleaned everything, removed any corrosion and carefully tinned the traces along the damaged areas. Some traces had to be repaired with thin wires.
I removed the keyboard socket for better cleaning and I also had to remove and replace the 2 ISA slots.

Damages caused by barrel batteries can be very treacherous, you never know where the liquid / gases have gone in between the layers of the board. Some traces look perfect but they do have very thin interruptions.

I bet there are still some damaged traces on your board!

I have replaced the ISA slots in the meantime, replaced the battery with a 4F 5.5V supercap and flashed the latest BIOS for support of larger harddrives.
Everything is working perfectly now.

majestyk wrote on 2021-02-25, 11:50:

Damages caused by barrel batteries can be very treacherous, you never know where the liquid / gases have gone in between the layers of the board. Some traces look perfect but they do have very thin interruptions.

I bet there are still some damaged traces on your board!

Awesome, thank you for the tips. Can you please also share photography of the underside of your board around the CMOS battery area please?

Sure. But remember it´s a different revision / version.

Whenever you see colorations, bubbles or spots on the copper-trails, you should remove the coating and the dirt carefully until the copper is shiny everywhere, clean everything, tin the traces for protection, measure the conductivity to all endpoints, repair with wires, if the solder won´t bridge the gaps.

If you intend to replace the battery by any recharable battery or a supercap, you need to replace the "charging-resistor" R3 also (470 Ohms).

The contacts of that 8-bit ISA slot don´t look too good also.

assasincz wrote on 2021-02-25, 11:10:

From SPK, I get series of 3 long beeps, approx 2 sec apart, series repeating after approx 5-6 secs. I am however not familiar wi […]
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From SPK, I get series of 3 long beeps, approx 2 sec apart, series repeating after approx 5-6 secs.
I am however not familiar with error beep codes on this board, and could not find any info on them

Could this be related to the fact that there are no L2 Cache chips on-board?
From the manual, there is not setting that disables L2 cache completely.

This sounds like RAM detection error. Double check memory modules, jumper settings or traces around the battery area.

It might be much easier. You always have to populate BANK0 first, then BANK1.
So if you want to use just 4 (identical) sticks of RAM they must be put in the OUTER 4 slots at the edge of the board, otherwise it won´t start up!
The 4 sticks are sitting in the wrong positions here.

majestyk wrote on 2021-02-25, 13:02:

Sure. But remember it´s a different revision / version. […]
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Sure. But remember it´s a different revision / version.

409_back2.JPG

Whenever you see colorations, bubbles or spots on the copper-trails, you should remove the coating and the dirt carefully until the copper is shiny everywhere, clean everything, tin the traces for protection, measure the conductivity to all endpoints, repair with wires, if the solder won´t bridge the gaps.

If you intend to replace the battery by any recharable battery or a supercap, you need to replace the "charging-resistor" R3 also (470 Ohms).

The contacts of that 8-bit ISA slot don´t look too good also.

I already ran a wire from external battery connector pin 1 so now it has good continuity all the way to solder point highligted -the trace is at some plqces completely eaten away -, and from then to (I presume) clock circuit. The external battery connector pin 4 is shorted to ground. So I guess its okay. Didnt try with external battery connected, but that should not prevent it from posting. Other wires were not necessary, I dont intend to run an internal battery at any point, only external. I checked all other visible traces, legs of bios chip and despite some corrosion, there is continuity where I can reach

I also already tried to swap the ram banks, still same behavior. I will try and switch few other SIMMs around, but in the meantime - still, could it be the cache chip issue? Can the board post without them in place, when there is no jumper to disable external cache?

In the manual there´s no jumpering for 0KB of cache. But I don´t think the absence of cache will prevent the board from starting - as opposed to the presence of faulty cache chips.
In most similar cases there finally was one interrupted trace left that I had forgotten to measure or that was hidden under some component.
Places like this:

You have to be extremely diehard here.

An update - the poor old goat lives!
The bank o is misidentified in diagrams, but I tried swapping that previously, so that was not the culprit. I applied some contact cleaner around, maybe that helped? External CMOS battery (3xAA) works, setting hold.
Im gonna fiddle around a bit more 😀

Could you make a BIOS image dump ? We don't seem to have version 2.0 archived on uh19.

http://www.win3x.org/uh19/motherboard/show/4435

computerguy08 wrote on 2021-03-06, 12:16:

Could you make a BIOS image dump ? We don't seem to have version 2.0 archived on uh19.

http://www.win3x.org/uh19/motherboard/show/4435

I am so sorry, even if I knew how to make the Bios image dump, the board is already gone, I built a full system around it into a restored case and sold it a few hours after posting it...