The only info I find is an ebay auction referring as:

Molecular Dynamics PBA 620028-204 Board for Storm 840 Phosphor Imager

But when I search for "Storm 840 Phosphor Imager" I get images of something like a scanner, nothing attached to that motherboard.
Here you can see it with a most modern computer.

Looks like an OEM version of this Intel 420ex board:

https://theretroweb.com/motherboards/s/intel- … ic-pci-ed-ninja

All the major component placements look the same. It's the same chipset configuration. Cache and etc/Dallas chip are in the same place.

All your cache sockets are empty, the heatsink is likely on a voltage regulator to convert 5v supply down to ~3.3v for the later 486 series of processors.
Looks to have built in fdd/ide which is a bonus on a 486 class system.

Early Intel 486 PCI chipset, smd caps, Im not a fan. Might be very problematic.

Agree rasz_pl. And with a soldered BIOS chip is PIA if eeprom goes bad, would think Intel would have taken the same care as most other retail motherboard makers and socket it.

I don't know the Kalex brand, but the 94V-0 is a standard of some kind. You'll find it on most boards of the era.

megatron-uk wrote on 2024-03-15, 20:23:

Looks like an OEM version of this Intel 420ex board: […]
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Looks like an OEM version of this Intel 420ex board:

https://theretroweb.com/motherboards/s/intel- … ic-pci-ed-ninja

All the major component placements look the same. It's the same chipset configuration. Cache and etc/Dallas chip are in the same place.

All your cache sockets are empty, the heatsink is likely on a voltage regulator to convert 5v supply down to ~3.3v for the later 486 series of processors.
Looks to have built in fdd/ide which is a bonus on a 486 class system.

Thank you !!!! really impressed of you guys !

debs3759 wrote on 2024-03-16, 02:39:

I don't know the Kalex brand, but the 94V-0 is a standard of some kind. You'll find it on most boards of the era.

iirc someone in another thread trying to ID a board with a similar mark said it was something to do with the manufacturing process. Either board type/material or code for the PCB maker.

debs3759 wrote on 2024-03-16, 02:39:

I don't know the Kalex brand, but the 94V-0 is a standard of some kind. You'll find it on most boards of the era.

Very interesting:

What does the 94V-0 rating mean?

The 94V-0 rating is a standard classification used to determine the flammability of a material, specifically in the case of prin […]
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The 94V-0 rating is a standard classification used to determine the flammability of a material, specifically in the case of printed circuit boards (PCBs). Underwriters Laboratories (UL), an independent safety consulting and certification company, developed this classification system to ensure the safety and reliability of electronic devices.

The "94" in 94V-0 refers to the vertical flame test, where a sample of the material is exposed to an open flame for a specified duration. The "V-0" indicates the highest level of flame retardancy, meaning that the material self-extinguishes within 10 seconds and does not generate flaming drips.

The 94V-0 rating is crucial in the design and selection of PCB materials, as it determines the level of fire resistance and safety in various applications. It ensures that electronic devices meet stringent safety standards and reduces the risk of fire hazards.
Advantages of using the 94V-0 circuit

The 94V-0 circuit offers several advantages that make it a preferred choice for electronic device manufacturers. One of the key advantages is its superior flame retardancy, which enhances the safety and reliability of electronic devices. The self-extinguishing property of the 94V-0 circuit ensures that any fire incidents are contained and mitigated quickly.

Additionally, the 94V-0 circuit provides excellent electrical insulation properties, preventing short circuits and enhancing the overall performance of electronic devices. Its high dielectric strength and low moisture absorption make it suitable for a wide range of applications, including automotive, aerospace, and consumer electronics.

Moreover, the 94V-0 circuit is compatible with automated assembly processes, allowing for efficient and cost-effective production. Its compatibility with lead-free soldering processes further contributes to environmental sustainability and compliance with regulatory standards.

debs3759 wrote on 2024-03-16, 02:39:

94V-0 is a standard of some kind

non flammable PCB substrate 😀
edit: zzgus already pasted detailed description above