VOGONS


First post, by Marco

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Dear all,

My old 386sx vlsi 311 rev.1 board won’t boot up after x years in my shelf.

The psu doesn’t really starts running - no fan no CD-ROM drive spin up etc. no matter if with ram, cards or without. I also feel like smelling bit of burned smell/torch.
I also notice that one of the capacitors flashs a bit blue when turning power on. It’s the one in the middle of the picture attached.
Could this be the reason? Replace it?
What else?
I read a lot about “cleaning” the mb which I just did so let’s see what comes out.

I am looking forward to any idea from you colleagues.
Thanks

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Reply 1 of 12, by quicknick

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Light-emitting capacitor, that must be a new device 😀
It's internally shorted, tantalum caps tend to do this, replace it before it explodes and makes a mess in the area. You can test the board after removing it, but in the long term it's better not to leave that spot empty.

Also, if that's the original battery, replace it ASAP. You're in luck, there seems to be no corrosion so far, though the picture is kind of small, so if you notice any green goo underneath the battery you must neutralize it with vinegar then rinse the area.

Reply 2 of 12, by Marco

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Dear quicknick

So I just cut that one off? Do I shortcut? I assume not 😀))

Here again a better view:

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Reply 3 of 12, by TheMobRules

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Just remove the capacitor, don't short the points afterwards or you'll have the same problem! The power supply refuses to turn on precisely because the cap is shorted, and you want to remove that short.

If it works after removing the cap and you want to keep using the board, I recommend replacing all of those blue tantalums, not just the one you removed.

Reply 6 of 12, by kalohimal

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I had the tantalum caps exploded on me several times before, once the debris flying out nearly hitting my eye (I closed my eyes immediately and it hit my eyelid). Nowadays I wear safety glasses when powering up old boards that had been in storage for a long time. Btw, is the pin header near the battery suppose to have a jumper on it? They are usually for external battery, but I could be wrong though.

Slow down your CPU with CPUSPD for DOS retro gaming.

Reply 7 of 12, by maxtherabbit

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kalohimal wrote on 2020-07-07, 03:37:

I had the tantalum caps exploded on me several times before, once the debris flying out nearly hitting my eye (I closed my eyes immediately and it hit my eyelid). Nowadays I wear safety glasses when powering up old boards that had been in storage for a long time. Btw, is the pin header near the battery suppose to have a jumper on it? They are usually for external battery, but I could be wrong though.

often times they used the jumper on the center pins of the external battery header to enable the onboard battery

just chop off the barrel, remove the jumper and plug in ext batt zoom

Reply 10 of 12, by cliffclaven

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Marco wrote on 2020-07-07, 05:35:

Good morning thanks will do. already have my external battery pack plus connector in my shelf. More to come

I have the same board, with barrel battery, and center pins (2 and 3) jumpered. Do you know which pins to connect for an external battery pack?