What type of RAM did you install?

Most 486 motherboards will not boot with 72-pin EDO RAM installed. Try using FPM RAM.
Refer to the manual in terms of the memory configurations supported (single banked vs double banked).

Also ensure that your particular BIOS version supports the CPU you have installed (earlier BIOS revisions did not support the 5x86 CPU's).

Once you've covered the above, try booting with a minimum configuration (basically just using a 16-bit ISA graphics card) and then work your way from there.

If the board still doesn't show any signs of life, then you might have a defective BIOS ROM - you will then need to burn a new one.

It's actually not that simple. Just about anything could cause the board not to post or beep. Of course, you should start in the most obvious places to rule those out first.
In the worst case there could be damage to the silicon or PCB, which for most people means the board is not salvageable.

Recently I had a similar problem with a 486 PCI board of mine. I have not been able to repair it yet, but after a lot of troubleshooting I determined that the soldering on some of the chipset pins had come undone. I have seen this happen on a couple of my VLB cards too. This is just what happens when you're dealing with 25+ year old hardware.

Anonymous Coward wrote on 2020-09-04, 15:44:

It's actually not that simple. Just about anything could cause the board not to post or beep.

Couldn't agree more - my suggestions were based on past experience and what could be a possible cause of the problem, but these are definitely not the only issues that might be present.
The OP could also try testing the voltage output while the motherboard is switched on to see if there isn't perhaps a short on one of the rails.

So after flashing an image on the bios chip with my programmer somehow the board bootet up with the 486 DX2 66. Somehow it seems the graphic card I used is dead....
Like I said, I got it running with the 486DX2 66 but I was not able to boot it up with neither my AM5x86 P75 nor my overdrive DX4ODPR100. It neither boots up nor gives any beep codes. Tried already different jumper settings but still same result.... This board just has an incredibely high number of jumpers.

Anyone with the same board and the CPUs I am trying to get running?

What revision of the board do you have? I have a 1.22 that I have to troubleshoot and a 1.8 that works and has ben tested so far with Cyrix 5x86 133, AMD 5x86 P75 and TI 486 DX4-100. I got the CPU jumper settings from http://gboeger.de/Computer/Asus_PVI486SP3/pvisp3-cpu.html in case you haven't seen it yet. I'm still looking for a complete copy (paper or digital) of the manual. I was told in another thread that it also accepts faster EDO RAM, so will be testing that in a few weeks. Waiting for faster cache chips if they aren't fake 😀

Attached the jumper settings (scanned from the manual).

The rest of the files (drivers, jumper settings, etc.) I downloaded over the years.

Also check what chipset revision you have.

I've got the got same board running with a 5x86 P75 (at 133MHz).

The manual doesn't say which jumper settings to use for a 5x86 but one of the Asus support pages, which I see are included in the zip posted by @jesolo, does. You can find them in "CPU Upgrade & Jumper Settings for later revisions.mht" in the "Manual" directory (edit: Ah, @debs3759's link is the same page)

I haven't been able to get the board working with EDO RAM btw. If I remember correctly it didn't respond at all with EDO, no beeping or anything.

I tried the jumper settings on the linked homepage but the system wouldn't boot up. It's only booting up with the 486 DX2 66. I double checked and the RAM installed is FPM. Totally weired...

What revision is your board, and does it have the latest BIOS from the zip file jezolo posted above? BIOS 3.06 works for me on board revision 1.8. Going to try booting revision 1.22 with a DX2 this week, and update the BIOS to see if that will then boot with a DX4 or 5x86.