I have a seemingly rare 486 motherboard which shows no signs of life.
The Motherboard is marked with the labels B887 / 8 / 9 AI, which seems to be a Mecer branded board.
With an AT power supply hooked up, the power supply turns on but the board does not post, there is no beep and there is nothing displayed on the post analyser card, whether it's plugged into a PCI slot or an ISA slot.
I found a thread on Vogons of someone else who had the same board in working condition.
What I've tried so far: (In each case, the symptoms remain unchanged as above)
- Matched the jumpers on my board with the jumpers from the board on Vogons
- No memory installed / 1 module installed and tested through each of the slots / All slots populated with memory
- Tested an Intel DX4 75, DX4 100 and AMD DX4 100 as well as a Cyrix DX2 66. (I know all of these processors work because they work in my other 486 boards) I tested at 3.3V for the Intel and AMD processors and 3.45 as well as 4V for the Cyrix. (All ongoing testing is with the Cyrix DX2 66)
- With the processor removed, measured the voltage in the socket while changing the voltage jumpers and noted that the voltage changed with each jumper change as follows: (Measuring pin as shown in attached image marked with red dot)
Jumper 3.3V position - 3.5V
Jumper 3.45V position - 3.8V
Jumper 4.0V position - 4.1V
Jumper 5.0V position - 5.1V
- Noted that all processors installed do get warm and even hot over time. (The Intel processors get quite hot over time, like 3-5min but the other processors only get warm)
- Examined the board under my digital microscope to check for damaged components or broken traces. Found some scratches of the mask but the traces measured continuity so I just tinned the traces and confirmed no shorts. (Near to the SMC chip) The board is otherwise in really neat condition.
- Washed the board with dish soap and warm water and dried with a blower until no more visible moisture and then left over night to dry further. (Removed the BIOS chip, CMOS battery and CPU lid before washing)
- Removed the BIOS module and saved the BIOS using TL866 3G / Flashed another BIOS from The Retro Web and then tested and then back to the original BIOS (No change in symptoms)
- Noted that the reset LED on the post analyser flashes at power on and then turns off. (The -12V, +12V and +5V LEDs remain on while the power is tuned on)
I have a digital multimeter and a post analyzer card, I do not have an oscilloscope or any other advanced electronics equipment.
I am handy with a soldering iron and capable of replacing components but I do not have much electronics knowledge and experience, and do not know how to trace the fault and repair it.
I am requesting step-by-step guidance on troubleshooting this board with the hope of fixing it.
The Motherboard is marked with the labels B887 / 8 / 9 AI, which seems to be a Mecer branded board.
With an AT power supply hooked up, the power supply turns on but the board does not post, there is no beep and there is nothing displayed on the post analyser card, whether it's plugged into a PCI slot or an ISA slot.
I found a thread on Vogons of someone else who had the same board in working condition.
What I've tried so far: (In each case, the symptoms remain unchanged as above)
- Matched the jumpers on my board with the jumpers from the board on Vogons
- No memory installed / 1 module installed and tested through each of the slots / All slots populated with memory
- Tested an Intel DX4 75, DX4 100 and AMD DX4 100 as well as a Cyrix DX2 66. (I know all of these processors work because they work in my other 486 boards) I tested at 3.3V for the Intel and AMD processors and 3.45 as well as 4V for the Cyrix. (All ongoing testing is with the Cyrix DX2 66)
- With the processor removed, measured the voltage in the socket while changing the voltage jumpers and noted that the voltage changed with each jumper change as follows: (Measuring pin as shown in attached image marked with red dot)
Jumper 3.3V position - 3.5V
Jumper 3.45V position - 3.8V
Jumper 4.0V position - 4.1V
Jumper 5.0V position - 5.1V
- Noted that all processors installed do get warm and even hot over time. (The Intel processors get quite hot over time, like 3-5min but the other processors only get warm)
- Examined the board under my digital microscope to check for damaged components or broken traces. Found some scratches of the mask but the traces measured continuity so I just tinned the traces and confirmed no shorts. (Near to the SMC chip) The board is otherwise in really neat condition.
- Washed the board with dish soap and warm water and dried with a blower until no more visible moisture and then left over night to dry further. (Removed the BIOS chip, CMOS battery and CPU lid before washing)
- Removed the BIOS module and saved the BIOS using TL866 3G / Flashed another BIOS from The Retro Web and then tested and then back to the original BIOS (No change in symptoms)
- Noted that the reset LED on the post analyser flashes at power on and then turns off. (The -12V, +12V and +5V LEDs remain on while the power is tuned on)
I have a digital multimeter and a post analyzer card, I do not have an oscilloscope or any other advanced electronics equipment.
I am handy with a soldering iron and capable of replacing components but I do not have much electronics knowledge and experience, and do not know how to trace the fault and repair it.
I am requesting step-by-step guidance on troubleshooting this board with the hope of fixing it.
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