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Help! Micronics/Gateway 2000 486 Motherboard Mysteriously Dies

Hugo Holden said:
...also don't forget this remark I made about doing it; "Saturate the area with CRC's CO contact cleaner and brush between the pins".

It is not a good idea to brush dry IC pins. When it is saturated with the cleaner it prevents and electrostatic charges building up. Though it is much more risky to dry brush IC pins out of circuit than in/on a circuit board, because normally, in circuit, there are no floating input pins.
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I will keep this in mind and report back. Thank you for all the advice.

How does this brush look?
 

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Hi all,

I tried the contact cleaner/brush and the deionized water technique. Neither worked. I’m back to square 1 now, getting the [02][--] and those stupid long tones. I am beyond frustrated with this board and will be actively searching for a replacement. Thank you to all who have tried to help me. Your help was greatly appreciated.
 
Alright, not giving up yet:

I installed the latest BIOS I could find for this board, and now I get a definitive beep code, with no video. The BIOS is PhoenixBIOS 4.05.05, and the code I get is 1-4-2-1. Looking it up, this says “CMOS RAM read/write failure (this commonly indicates a problem on the ISA bus such as a card not seated correctly).” I’ve tried booting the board with no ISA cards and I get the same beep code. So it looks like there may be a problem on the ISA bus. I have another type of this board in a similar system I can use to compare things, but I have no clue what it is I’m looking for. I have little experience with a multimeter and am not sure where to start. Any advice would be greatly appreciated!

Thanks for all the help everybody. I’ve come too far on this board to give up now. Let’s hope we can revive it!
 
bostonvintage1993 said:
Looking it up, this says “CMOS RAM read/write failure (this commonly indicates a problem on the ISA bus such as a card not seated correctly).”
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"CMOS RAM" is sure to be referring to the small amount of RAM located within what is commonly referred to as the 'CMOS' chip (CMOS/RTC chip) - see [here]. That RAM is primarily used by the BIOS to store the 'CMOS SETUP' configuration information. It is used for other things as well.

( At [here], 'Verify shutdown byte in 146818 RTC chip' is the POST in the IBM AT testing a particular address in the subject RAM. )

The chip may be faulty, but perhaps the chip is good and the POST cannot communicate with it due to some other problem on the motherboard.
 
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Continuing on from my previous post:

From the photo in post #1, I see that the CMOS/RTC chip on your motherboard is a 146818. I presume that as part of your repair work, you have re-seated that chip in its socket.

For your interest, the diagram at [here] shows how the chip is implemented in the IBM AT.

One thing you could do is verify that +5V is reaching pin 24 of the 146818 when the motherboard is powered on.

I do not know if it applies to your motherboard's implementation of the 146818, but in the IBM AT's implementation, the 'chip enable' pin (pin 13) of the 146818 is held at a LOW state (i.e. 146818 always enabled).
 
Ok just to check, so you have an Eprom programmer ? I can give you a copy of the BIOS off the Dell board if you need it.
 
modem7 said:
Continuing on from my previous post:

From the photo in post #1, I see that the CMOS/RTC chip on your motherboard is a 146818. I presume that as part of your repair work, you have re-seated that chip in its socket.

For your interest, the diagram at [here] shows how the chip is implemented in the IBM AT.

One thing you could do is verify that +5V is reaching pin 24 of the 146818 when the motherboard is powered on.

I do not know if it applies to your motherboard's implementation of the 146818, but in the IBM AT's implementation, the 'chip enable' pin (pin 13) of the 146818 is held at a LOW state (i.e. 146818 always enabled).
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Hi @modem7,

Sorry for the late reply - life got in the way of my vintage computer repairs. Thank you very much for the documentation on how this chip works in the IBM AT - I find that very interesting. Currently, when I just returned to the motherboard, I can no longer even get it to boot the the BIOS flash screen, so I think the problem may be the BIOS chip and not the 146818. Thank you again for your reply.
 
twolazy said:
Ok just to check, so you have an Eprom programmer ? I can give you a copy of the BIOS off the Dell board if you need it.
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Hi @twolazy,

I'm sorry for the late reply, life has just got in the way of my work on vintage computers. I have returned to this board and I can no longer get the board to boot at all, not even to the BIOS FLASH recovery mode of the motherboard. So I'm thinking maybe the BIOS chip was bad all along. If you wouldn't mind, I would really appreciate a copy of the Dell BIOS to see if that particular BIOS fixes the board. I don't have an EEPROM programmer but would be willing to invest; do you have a recommendation for one?

Thank you again for all your help on this board, and sorry again for the late reply.
 
I believe I have the right adapter( PLCC 32 ) for my programmer, have to scrounge up an eprom for you, but I can help you with that so you don't have to buy a programmer.
 
twolazy said:
I believe I have the right adapter( PLCC 32 ) for my programmer, have to scrounge up an eprom for you, but I can help you with that so you don't have to buy a programmer.
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Hi,

That is very kind of you. Thank you for doing that for me. Hopefully with a new eprom the board can be revived. There is no rush, just let me know when you find the time to make one.

Thank you again!
 
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