I recently got this Micronics 386 ISA board from another member because it was dead from battery damage, he had performed repair […]
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I recently got this Micronics 386 ISA board from another member because it was dead from battery damage, he had performed repairs but it still wouldn't POST. I believe the board matches this one.
I have tinkered with it a bit, I have tried a different BIOS, reseated many chips and done an assortment of other things. I am able to get POST codes out of it on my diagnostic cards, and some things I have done have gotten the numbers to go higher but I can't really make sense of what it's doing beyond that.
From the speaker I get what seems like 4 short beeps (they blend together) followed by 2 more beeps spaced out evenly.
Anyway, I'm not going to expect anyone to diagnose it for me, but I have discovered a questionable component on the board that I don't have a lot of experience troubleshooting.
I was using my Fluke75 meter in diode test mode (it should beep once in one direction on diodes, with no beep going the other direction), and one of these diodes gives no beep at all. It also seems like it might be cracked around the middle (I can feel it with my fingernail, and through a magnifier it looks cracked), which seems strange. I have marked it with a red arrow.
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EDIT: Confirmed, it is totally cracked in half! When I poke and prod the poor thing the ends move independently, so it definitely needs replaced.
I'm clueless about identifying diodes, but I have these on hand that look similar: 1N4148 and 1N4733A
If anyone can help me identify that diode and whether the ones I have on hand will replace it that would be a huge help.
Also, I have checked for continuity and shorts involving the repairs the previous owner made and they seem fine, so I don't believe that is what is preventing the board from booting.