VOGONS


First post, by whitepawn

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Hi,
I just saved FIC 486-PVT Doc:14060 from an electronics junkyard about 6$.I/O board was missing though.Anyway i went to home and cleaned board and measured AT power pins before plugged it in.Found out -12v rail is shorted to ground.After some poking around with a multimeter i found out that CB11 capacitor is shorted.Replaced it with 100nf polyester capacitor and short is gone.Then i downloaded manual for this board from an ftp site and installed cpu (A80486DX2-66) and set jumpers according to manual.

When i power on system without ram it beeps continuing on single tone which seems ram issue obviously.Then when i install EDO rams and power on system doesn't beep but also doesn't post either.I know my graphics card (HM86304Q) and rams are fine i have tested it on another machine.So could anyone have any suggestions?

Another question i have also Cyrix Cx486-DX2 66 and AMD Am486 DX4-100 which may required regulator board according to manual.If i solder Q2 and R49 will it support these cpus or separate regulator board is needed?Are there any DIY solution or any picture of this regulator boards available?I have searched online and found only this info FIC 486-PVT Jumper Settings for 5 Volt CPUs which helped a lot to setup jumpers but my card is missing Q2.

Here is motherboard photos and manual for feature referance.
And here is whole dropbox folder:
https://www.dropbox.com/sh/dvh8i993a6ean76/AA … eIxndM28sa?dl=0

Thanks in advance.

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Reply 1 of 3, by Riikcakirds

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Do you have any fpm ram instead of edo. I would try an ISA Diagnostic POST Card (with 4-Digit display) too just in case their is another problem at post. You can get them for 3-4$ on that auction site. Does the vga output at all on an ISA video card.

Reply 2 of 3, by majestyk

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No EDO Ram supported. It´s FPM only due to MCH "VT82C496G".
Just check the datasheet.

Q2 is NOT the actual VRM, it´s just a switch to turn on the 5V core voltage .
When it´s not there, the 5V core voltage is configured with jumpers on the 16-pin block.
You do have the voltage regulater on board already that provides all the voltages from 3V to 3,45V . It´s all you need, no soldering, no additional VRM-board, no additional components needed.
Just jumper correctly and you can use a DX4 or Cyrix.

Reply 3 of 3, by whitepawn

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Riikcakirds wrote on 2021-03-04, 16:47:

Do you have any fpm ram instead of edo. I would try an ISA Diagnostic POST Card (with 4-Digit display) too just in case their is another problem at post. You can get them for 3-4$ on that auction site. Does the vga output at all on an ISA video card.

Good idea to have diagnostic post card.I will buy below one it has 4 digits i assume this works fine with diagnostics with 468 boards right?

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majestyk wrote on 2021-03-04, 17:08:
No EDO Ram supported. It´s FPM only due to MCH "VT82C496G". Just check the datasheet. […]
Show full quote

No EDO Ram supported. It´s FPM only due to MCH "VT82C496G".
Just check the datasheet.

Q2 is NOT the actual VRM, it´s just a switch to turn on the 5V core voltage .
When it´s not there, the 5V core voltage is configured with jumpers on the 16-pin block.
You do have the voltage regulater on board already that provides all the voltages from 3V to 3,45V . It´s all you need, no soldering, no additional VRM-board, no additional components needed.
Just jumper correctly and you can use a DX4 or Cyrix.

Oh i see very good to hear i taught i will need reguator board or Q2 i am relived thanks.I will try to find FPM ram and post results.Thank you.