Set JP 9/10/11/12 to 33 MHz...connect a speaker or a POST card...and POWER ON 😎

Predator99 wrote:

Set JP 9/10/11/12 to 33 MHz...connect a speaker or a POST card...and POWER ON 😎

Thanks for the response. What should I do with the cache jumpers?

486 DX2 work on most motherboards.

I've not yet seen a board that didn't POST without a battery, but I guess it can still happen.

Yes with video/ram and keyboard you will be able to view the POST screen and play with the bios settings. However of course if you want to boot you need a bootable device such as a HDD or a floppy drive.

If you manage to reach the POST screen, please send a picture of that screen because it can help to find the manufacturer

wacha wrote:

Predator99 wrote:

Set JP 9/10/11/12 to 33 MHz...connect a speaker or a POST card...and POWER ON 😎

Thanks for the response. What should I do with the cache jumpers?

Set to 64k...you will not damage anything if wrong.

Thank you all for your responses. I'll test it and see if it boots. Maybe we can figure out the manufacturer that way.

Cheers.

Hi guys. Sorry for not reporting earlier, but I haven't been able to test the motherboard yet because the ATX to AT power supply adapter I bought came without an on/off switch. I have ordered another one but it may be still two weeks before it arrives.

Can I start the system without the switch? Something like shorting the power pins in ATX motherboards but with the AT cables?

Here's a picture of the ATX to AT adapter:

https://drive.google.com/file/d/1ls3crb3MzqOS … iew?usp=sharing

Thanks in advance guys, much appreciated.

wacha wrote:

Can I start the system without the switch? Something like shorting the power pins in ATX motherboards but with the AT cables?

Yes, short the 2 cables...

Hi guys. Sadly, I think the mobo is dead.

The power supply turns on as soon as I short the two cables, and will remain on until they stop touching. I have tested this by attaching a fan to the power supply. However, the motherboard clicks once after powering on, and then nothing. The keyboard lights turn on for about a second and then they turn off again and I have no video signal nor any kind of sound coming from the speaker. Once the keyboard lights are off, the motherboard makes the sound other motherboards do during POST, but still, no beeps, no keyboard lights, no video signal. I have tested with both my ISA and VLB video cards. I can confirm the RAM is working as is the keyboard.

Just in case, I will recap the configuration:

J1, J2, J4, J5 set to 64k
J6, J7 set to 486
J8 open, as it came. It reads: SHORT DISENABLE PQFP 486SX. I suppose open is the right choice por a 486 DX2
J9, J10, J11, J12 set to 33 MHz

And a picture:

https://drive.google.com/file/d/1-TJi9kqSsAx8 … iew?usp=sharing

Thanks guys.

Any shortened pins on the bottom side?

What sound does the motherboard do during POST without a speaker..? This is unusual...

486 MBs are very picky with 72-Pin RAMs. But you should hear a beep even without RAM.

Think for further diag you need a POST-card - 3€ from China.

wacha wrote:

...the motherboard clicks once after powering on
I have no video signal nor any kind of sound coming from the speaker.
the motherboard makes the sound other motherboards do during POST, but still, no beeps

Am i going crazy or what? 😖

Predator99 wrote:

Any shortened pins on the bottom side? […]
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Any shortened pins on the bottom side?

What sound does the motherboard do during POST without a speaker..? This is unusual...

486 MBs are very picky with 72-Pin RAMs. But you should hear a beep even without RAM.

Think for further diag you need a POST-card - 3€ from China.

GigAHerZ wrote:

wacha wrote:

...the motherboard clicks once after powering on
I have no video signal nor any kind of sound coming from the speaker.
the motherboard makes the sound other motherboards do during POST, but still, no beeps

Am i going crazy or what? 😖

Well, what I mean with "that sound" is when it's checking for devices like Floppys or HDDs, I can usually hear noise just before the floppy disk sound. I can't really describe it as English is not my native language, it's always been a sound I asociate with powering an old computer. Never mind, I´ll get a POST card from China and report back, but shipping's gonna take a while. I'll check again to see if I see any shorted pins, though that's the first thing I checked when it didn't POST.

What I mean by click is exactly that, a click when current is first received. Not a beep from the speaker, but "click". Then keyboard lights for a second, then "that sound", then nothing.

Sorry if I didn't express myself correcly. Thanks for your help guys.

All of those are MB-4D33/50NR and MB-4D33/50NR-02 I think, not MB-4D33/50N.
ASI (Aquarius Systems Inc) seems to have a weird way of numbering their boards. I'll see if I can dig up some jumper settings.

https://www.ultimateretro.net/en/motherboards/5451