This means it has been already reflashed during bios recovery procedure I performed, I guess
unless recovery routine only recovers main bios region and keeps video bios region intact

I just got a Packard Bell 486 computer with a PB 450 motherboard in it, which works, would it be helpful if I took some pictures of the jumper configuration on my one?

Also which CPU is in your one? Mine has an ST 486DX-80 in it, though for some reason, the motherboard is insistent that it's a 486 DX4 100MHz, regardless of the multiplier I set or the FSB (25 or 33)

edit: that video helps, the double beep reminds me of when I initially set it up with no CMOS battery connected (since the inbuilt lithium failed long ago) - Once I put a 3v lithium coin cell between pins 1 (+) and 4 (-) of the battery connector, that helped.

Have you tried a different monitor? I noticed the BIOS has settings for the refresh rate & display type of the monitor connected, maybe it's picky

I'm pretty sure the jumper settings are correct. My CPU is 486 dx2-66 Mhz
Can you please try to disable the on-board video (J19) and try to start the motherboard. I wonder if you get two beeps like me.

Thermalwrong wrote:

edit: that video helps, the double beep reminds me of when I initially set it up with no CMOS battery connected (since the inbuilt lithium failed long ago) - Once I put a 3v lithium coin cell between pins 1 (+) and 4 (-) of the battery connector, that helped.

That's the first thing I tried after replacing the memory, and it did not help.
May be I should try again

Tried again to connect external battery
Also tried with no monitor connected, will try another monitor later
still the same two beeps

ahtoh wrote:

Is it possible that Video bios is located in the same socketed chip where the main bios is?

I'm sure it is there. 8242 is KB/MS controller

But if you make MS-DOS boot floppy will it boot?
I think there are utilities that can boot VGA bios from file on disk. So we could eliminate onboard VGA bios (in case if it's wrong)...

Roman555 wrote:

But if you make MS-DOS boot floppy will it boot?

No

I'm now trying to source an ISA graphics card and also ordered a POST tester card like this one https://www.ebay.com/itm/For-4Digit-PC-Comput … 872.m2749.l2649
I wonder if the POST tester may differentiate between video memory error and video chip failure.
In this case I would be probably be able to swap some chips from another board.
Not sure if I can replace cl-gd5428 with cl-gd5424 though

ahtoh wrote:

I was able to flash the bios using built-in recovery routine (using J17)

During bios-recovery procedure (J17) was a new bios file loaded from a floppy disk (autoexec.bat with phlash.exe)? I ask because boot-block jumper bios-recovery usually is done with help of a crisis floppy disk. So this suggests me that the system would be loaded to MS-DOS from a floppy (onboard video disabled, blindly press some keys on keyboard after two beeps to make loading goes on).

there is no such files (autoexec.bat phlash.exe) on the recovery disk
here is the content:
it comes from PB450RD.EXE which can be downloaded here http://files.mpoli.fi/hardware/ROM/OTHER/?C=N;O=D
oldbios.bin file size is 128Kb, that matches the 28F001BX-T bios chip size http://www.lyr-ing.com/DocumentosLyR/EXT/ICs/ … tFlashEPROM.pdf

Did you try the PB450ISA.ZIP file?

Nope.
But I was able to boot from the Floppy drive!

I pressed F1 as you suggested and it looks like it started booting from the FDD.
I don't see anything on the screen though.

Odd. Also, the autoexec.bat file is always hidden in Windows 9x and higher anyway. Try typing in bbcmd.com blindly and type Y for yes. Once done, the PC speaker will beep 6 times and the FDD light would turn off. Power off the desktop and remove the diskette drive. Funny thing is, your monitor has a green light on, but doesn't say no signal. Looks like oxidation on the VGA port of the motherboard.

Also, the 2 beeps indicate BIOS settings were reset to their default values as well, and once you press F1, it beeps once and continues on. Sounds like you're getting further (might be a BIOS slight corruption).

I think I should have mentioned I used just random bootable floppy, not the one I used for recovery with J17

this is getting interesting...

I'm NOT able to boot with a monitor connected (tried two different monitors)
It looks like the system is booting from the floppy without monitor connected, but when I try to type "DIR" and hit enter I hear no drive drive seeking.

Ah. At least you know the board isn't fully dead, though.

Maybe the PSU might be losing voltage. Could be a possibility, and there are PSU kits available that'll allow you to use an ATX PSU as an AT PSU (with the -5VDC and dummy load). I'm planning on purchasing one on eBay sometime soon as well.

The PSU is fine. I checked with voltmeter.

Tried another boot disk (dos 6.22) - same thing. It starts loading but then freezes and do not respond on keys.

I'm getting inconsistent results.
Now I'm not able to start booting, even with no monitor connected.

Check the capacitors for any leakage. Do you have a hard drive or CD drive hooked up? If so, disconnect the drive(s).

There are a few items that can cause a system lock-up:

1) Dried or leaked capacitors
2) I/O going out (FDD/HDD/KB/Mouse)
3) Ribbon cable for the FDD being either too lose or oxidized
4) Incorrect CPU voltage (highly unlikely since the PB450M boards only support 5V CPUs)
5) Bad cache chips (like mine, not installed, so, unlikely)
6) Dead battery (you have an external hooked up, so that's not possible)
7) Incorrect BIOS setup (FDD might be set to 5.25 1.2MB FDD instead of 3.5 1.44MB FDD, but, that depends on if you have one installed)
8) Corrupt Video BIOS*

* In the same BIOS chip that houses the PC's main BIOS.

I visually checked capacitors and they look good. I do have an ESR meter, may be it is worth checking.
The only drive connected is FDD, and it is 1.44
I disconnected the external battery after I figured out it is not solving the problem so I'm now back with the dead battery.