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386/486 build in a mini ATX case ?

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First post, by Jester

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I recently bought this older mini ATX desktop because it has a bit of a retro Packard Bell look. Only one of the standoffs that support the motherboard line up with the holes on a baby AT motherboard, so I will need to improvise to make ends meet by drilling and threading some needed standoffs and plastic legs where needed so I don’t flex the mobo or short it out when swapping Isa cards. I also plan on putting a turbo mhz led display in there either where the usb port is on the bezel or just in the 3.5” or 5.25” bay cover.

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Perhaps a bigger issue is that the matx power supply that works with the matx board does not give any response when plugged into the 486 board through the p8/p9 conversion adapter. According to the internet, it’s the same as any other ATX psu, just lower wattage, so I’m puzzled why it doesn’t power on.

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Reply 2 of 5, by HanSolo

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No need to drill anything. Just use some plastic spacers to keep it away from the metal plate. The board is held in place by the ISA cards and the one metal standoff.

I mean these things

Reply 3 of 5, by Jester

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HanSolo wrote on 2023-09-10, 19:04:

No need to drill anything. Just use some plastic spacers to keep it away from the metal plate. The board is held in place by the ISA cards and the one metal standoff.

I mean these things

True. That would suffice if I wasn’t the type that is constantly swapping out different video cards. Adding and removing those long vlb cards especially put some torsion on the mobo. I’m voting for at least two standoffs plus the plastic legs, minimum.

Those existing supports will need some kind of insulating material too to prevent contact. Screws in the day used to have those orange spacer rings .. they might be good enough.

Reply 4 of 5, by wierd_w

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486 board might need legacy -5v, which modern atx psu does not supply.

See also 'voltage blaster' and pals.

Additionally, a hard toggle switch is required for the poweron signal, to keep the atx psu active.

There is also a 3d printable AT keyboard 'form card' here on vogons. Give me a bit to find it.
Here you go:
ATX I/O shield models for 3D printing

In regards to the screw situation, I ordered a bunch of nifty 2.9mm white plastic shims/bushings from amazon for a retro project. If you cram the little neck of the bushing down the hole in the baked-on stand-off provisions, they should very effectively insulate the motherboard from contact.

https://www.amazon.com/Ochoos-1000PCS-Insulat … a_rpt_ba_s_0_sa

Reply 5 of 5, by Horun

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Perhaps a bigger issue is that the matx power supply that works with the matx board does not give any response when plugged into the 486 board through the p8/p9 conversion adapter. According to the internet, it’s the same as any other ATX psu, just lower wattage, so I’m puzzled why it doesn’t power on.

Actually the "probably fake" micro ATX PSU Powmax is labeled 300watt where the older better quality SPI that does work is 250watt.
The original Leadman Powmax PSU have a label like this: https://i.ebayimg.com/images/g/2NIAAOSwIFVjzqTO/s-l1600.jpg
Nothing like your matx psu. What you bought is not a true Leadman Powmax IMHO and I would not trust it....just my opinion.

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

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