Welcome to the forum! 😀

A corrupted BIOS is generally possible but it would not be my first suspicion. With a machine that age it is always possible a component has failed short. This would often keep the PSU from creating stable voltages and result in the system powering up but not POSTing.

What troubleshooting steps have you done so far?
Have you tried starting the machine with no RAM and expansion cards installed?

Can you post pictures of your board?

Thanks for the welcome and quick response.
Not sure how i can upload photos but i will try.
I have removed the processor board from the main board but the result is the same, the power supply powers ip but no POST nor video. Also no error beeps.

Will try to upload some photos.

Thank you for the picture. It always helps to better understand what one's dealing with.
In this case I didn't realise the PC used a CPU board. Of course without that it simply can't POST.

Do you have a multimeter? Can you check the voltages on the PSU with just a hard drive connected?
It looks like the system uses a standard AT connector. If so this is a pinout for your reference: http://www.hilmanind.com/pinouts/atpwr.htm

I agree, first of all you should take a closer look at the PSU. If not all voltages show their nominal value, Just open it, clean it and take a picture of the PCB. It´s the #1 suspect.

Further I would temporarily remove the 4 additional Video-RAM chips and test if there´s some reaction. Depending on the quality some old RAM chips stored/used for a very long time can fail.
You can also try to use a seperate ISA or EISA graphics card, if there´s still no video with the WD onboard graphics.

On the CPU card there are 4 sticks of RAM. The contacts at the sockets could have become flakey by corrosion and ageing. Taking the sticks out and in a couple of times and cleaning everything might help.

Seems like you could populate this machine with up to 3 processor cards 😀

You did not specify which exact model you have of the power premium so here's a list of what we have in Ultimate Retro:
https://www.ultimateretro.net/en/motherboards … Power%20Premium

Some basic jumper settings are in there that might help you getting these to work again.

Thanks for all the suggestions. Will check the PSU and remove the video RAM and clean the contacts as suggested.

I am not good at the electronic side of things so please bear with me if there is anything beyond my ability.

Found some time to check things out. Looks like the PSU is ok.

5V 5.3
-5V -4.98
12V 11.8
-12V -11.78

So I switched with a known good PSU and plugged into the motherboard, no luck. The reset button seems to still work tough.

Removing the video RAM is the same thing....
Any other thoughts are welcome

Does this thing have a backup battery somewhere? Can´t find one onboard, maybe its an external one.

majestyk wrote on 2021-01-30, 08:12:

Does this thing have a backup battery somewhere? Can´t find one onboard, maybe its an external one.

Yeah, it's a big block of external battery. I have one similar AST Premium too.

If that is dead/low voltage the bios may do weird things. Did you check the in-circuit voltage?

hymok wrote on 2021-01-30, 01:29:

Found some time to check things out. Looks like the PSU is ok. […]
Show full quote

Found some time to check things out. Looks like the PSU is ok.

5V 5.3
-5V -4.98
12V 11.8
-12V -11.78

So I switched with a known good PSU and plugged into the motherboard, no luck. The reset button seems to still work tough.

Removing the video RAM is the same thing....
Any other thoughts are welcome

What are the voltages when the PSU is connected to the motherboard?