holoprox wrote on 2023-12-21, 21:08:

Bought recently a 486 MoBo. A 16v/10uF cap on the +12V rail exploded on first power, sorry for not having a spectacular video! […]
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Bought recently a 486 MoBo.
A 16v/10uF cap on the +12V rail exploded on first power, sorry for not having a spectacular video!

On the second powering it posted.
I changed the blown capacitor, it concludes the whole POST, BUT it wont load OS.

I tried running 5 different CF cards with proper settings in bios, trough 5 different I/O cards, tried using external XT-IDE BIOS (3 different variants), tried booting from floppy — same result: a blinking cursor 🙁

16 sec. video: https://youtu.be/irBTJqobTT8

Any advice at this point would be helphull!

How big is the size of the compact flash card? Did you try with one < 500MB?
Is the flash card recognized by the Bios? The video is not helpful.

EDIT: Sorry overlooked the first screen. So Drive C set to NONE most likely will not work.

CoffeeOne wrote on 2023-12-21, 21:18:

holoprox wrote on 2023-12-21, 21:08:

Bought recently a 486 MoBo. A 16v/10uF cap on the +12V rail exploded on first power, sorry for not having a spectacular video! […]
Show full quote

Bought recently a 486 MoBo.
A 16v/10uF cap on the +12V rail exploded on first power, sorry for not having a spectacular video!

On the second powering it posted.
I changed the blown capacitor, it concludes the whole POST, BUT it wont load OS.

I tried running 5 different CF cards with proper settings in bios, trough 5 different I/O cards, tried using external XT-IDE BIOS (3 different variants), tried booting from floppy — same result: a blinking cursor 🙁

16 sec. video: https://youtu.be/irBTJqobTT8

Any advice at this point would be helphull!

How big is the size of the compact flash card? Did you try with one < 500MB?
Is the flash card recognized by the Bios? The video is not helpful.

All the CF cards boot on a other pc's — 512/128/32mb and of course they were set to TYPE 48 or 49 with correct settings taken from the autodetect results on a different MoBo

Can you boot from floppy?
The ide card is known good?

EDIT: After looking at your video again (so it was helpful), I think the system just crashes after the POST. It does not even try to boot.
So I guess you are not able to boot from floppy either.
If I am right, the problem is not related to the compact flash card.

CoffeeOne wrote on 2023-12-21, 21:27:

Can you boot from floppy?
The ide card is known good?

NO i can not boot from a known good card-fdd-fd combination, and yes all I/O cards work in other systems!

I am sure it is NOT related to CF/I/O/FDD and i tried to turn off cache all i can think about, but no help 🙁

DIAG card says FF (POST done! booting)

holoprox wrote on 2023-12-21, 21:32:

CoffeeOne wrote on 2023-12-21, 21:27:

Can you boot from floppy?
The ide card is known good?

NO i can not boot from a known good card-fdd-fd combination, and yes all I/O cards work in other systems!

DIAG card says FF (POST done! booting)

I edited my answer. See above, so you have a more severe problem, useless to fool around with various flash cards.

OK, one more weird thing in your pictures.
The Bios shows 4MB RAM.
But you have 8 30pin modules?

post battery corrosion green solder joints dont look good, probably goes all the way under SIMM/ISA slots

CoffeeOne wrote on 2023-12-21, 21:42:

OK, one more weird thing in your pictures.
The Bios shows 4MB RAM.
But you have 8 30pin modules?

Photos and video made separately, tried to lower ram to evade possible problems, nothing helps 🙁

There is a photo (with the video card) with only 4 slots populated 😀

holoprox wrote on 2023-12-21, 21:55:

CoffeeOne wrote on 2023-12-21, 21:42:

OK, one more weird thing in your pictures.
The Bios shows 4MB RAM.
But you have 8 30pin modules?

Photos and video made separately, tried to lower ram to evade possible problems, nothing helps 🙁

There is a photo (with the video card) with only 4 slots populated 😀

You could try only the other bank with the 4 simms.
Most likely something on the board is damaged.
What happens when you start with no ISA I/O card at all, only the Video card?
Then you should get Floppy not found (because it is set in the Bios)

CoffeeOne wrote on 2023-12-21, 22:05:

You could try only the other bank with the 4 simms. Most likely something on the board is damaged. What happens when you start w […]
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holoprox wrote on 2023-12-21, 21:55:

CoffeeOne wrote on 2023-12-21, 21:42:

OK, one more weird thing in your pictures.
The Bios shows 4MB RAM.
But you have 8 30pin modules?

Photos and video made separately, tried to lower ram to evade possible problems, nothing helps 🙁

There is a photo (with the video card) with only 4 slots populated 😀

You could try only the other bank with the 4 simms.
Most likely something on the board is damaged.
What happens when you start with no ISA I/O card at all, only the Video card?
Then you should get Floppy not found (because it is set in the Bios)

Other banks are "BANK1" (assumed it's working only with "BANK0", tommorow will try this
Starting with NO I/O card gives floppy "not found floppy" error, the bios checks allways fdd (last thing to check after memtest - it runs the memtest 5 times by the way)
It fails the floppy test with a particular cable with 1 fdd end (with twisted portion of course).

holoprox wrote on 2023-12-21, 22:13:

Other banks are "BANK1" (assumed it's working only with "BANK0", tommorow will try this Starting with NO I/O card gives floppy " […]
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CoffeeOne wrote on 2023-12-21, 22:05:

You could try only the other bank with the 4 simms. Most likely something on the board is damaged. What happens when you start w […]
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holoprox wrote on 2023-12-21, 21:55:

Photos and video made separately, tried to lower ram to evade possible problems, nothing helps 🙁

There is a photo (with the video card) with only 4 slots populated 😀

You could try only the other bank with the 4 simms.
Most likely something on the board is damaged.
What happens when you start with no ISA I/O card at all, only the Video card?
Then you should get Floppy not found (because it is set in the Bios)

Other banks are "BANK1" (assumed it's working only with "BANK0", tommorow will try this
Starting with NO I/O card gives floppy "not found floppy" error, the bios checks allways fdd (last thing to check after memtest - it runs the memtest 5 times by the way)
It fails the floppy test with a particular cable with 1 fdd end (with twisted portion of course).

I do not understand your last sentence.
So without I/O card, it behaves correctly => floppy error.

And what happens with I/O card and only the floppy drive connected (No ide device connected)?

CoffeeOne wrote on 2023-12-21, 22:23:

I do not understand your last sentence. So without I/O card, it behaves correctly => floppy error. […]
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holoprox wrote on 2023-12-21, 22:13:

Other banks are "BANK1" (assumed it's working only with "BANK0", tommorow will try this Starting with NO I/O card gives floppy " […]
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CoffeeOne wrote on 2023-12-21, 22:05:

You could try only the other bank with the 4 simms. Most likely something on the board is damaged. What happens when you start w […]
Show full quote

You could try only the other bank with the 4 simms.
Most likely something on the board is damaged.
What happens when you start with no ISA I/O card at all, only the Video card?
Then you should get Floppy not found (because it is set in the Bios)

Other banks are "BANK1" (assumed it's working only with "BANK0", tommorow will try this
Starting with NO I/O card gives floppy "not found floppy" error, the bios checks allways fdd (last thing to check after memtest - it runs the memtest 5 times by the way)
It fails the floppy test with a particular cable with 1 fdd end (with twisted portion of course).

I do not understand your last sentence.
So without I/O card, it behaves correctly => floppy error.

And what happens with I/O card and only the floppy drive connected (No ide device connected)?

With a known good Floppy Drive, cable, diskette and controller it wont read - all tests good, but after going trough POST the floppy blinks once and stops!

holoprox wrote on 2023-12-21, 22:27:

CoffeeOne wrote on 2023-12-21, 22:23:

I do not understand your last sentence. So without I/O card, it behaves correctly => floppy error. […]
Show full quote

holoprox wrote on 2023-12-21, 22:13:

Other banks are "BANK1" (assumed it's working only with "BANK0", tommorow will try this
Starting with NO I/O card gives floppy "not found floppy" error, the bios checks allways fdd (last thing to check after memtest - it runs the memtest 5 times by the way)
It fails the floppy test with a particular cable with 1 fdd end (with twisted portion of course).

I do not understand your last sentence.
So without I/O card, it behaves correctly => floppy error.

And what happens with I/O card and only the floppy drive connected (No ide device connected)?

With a known good Floppy Drive, cable, diskette and controller it wont read - all tests good, but after going trough POST the floppy blinks once and stops!

So no more output on the screen, right?
Did you try all possible ISA slots for the I/O card?

CoffeeOne wrote on 2023-12-21, 22:33:

holoprox wrote on 2023-12-21, 22:27:

CoffeeOne wrote on 2023-12-21, 22:23:

I do not understand your last sentence.
So without I/O card, it behaves correctly => floppy error.

And what happens with I/O card and only the floppy drive connected (No ide device connected)?

With a known good Floppy Drive, cable, diskette and controller it wont read - all tests good, but after going trough POST the floppy blinks once and stops!

So no more output on the screen, right?
Did you try all possible ISA slots for the I/O card?

There is a blinking cursor on the screen, tried 3 different slots.

This morning a miracle happened — it booted from the 1st try.

The BIOS had lost all settings.

It turns out the single cause (after short investigation) was that it won't work with 1WS setting (it works with 2ws).
On the photos the setting is even 3WS, the non-booting problem may be caused by some older trash in BIOS, but there are no more setting screens?
Boots with 8mb ram(70ns), 256k cache, video & system shadowed & cached) from 512CF.