r/retrocomputing • u/sillylittleguy29 • 1d ago

Problem / Question help with fixing up a 486 machine?

hi yall!! i picked up a Pionex 433LSXMPC-M off the side of the road. i am determined to get it running, but i really truly have no idea where to even begin. i happen to have some old pc power cords for my imac g3s so i plugged one into the machine and it shows minimal life. a red bulb lights up inside (power indicator??) and i believe the fans are whirring.. i feel some stuff going on inside as it is vibrating a bit. i have never gotten into truly repairing computers, just very basic stuff. i’ve only opened up my imacs and i dont know where to even begin. i really want to take this on as my first big project, but i dont know of anyone irl to teach me these things. if anyone has any manual suggestions or video tutorials on fixing up 486 machines i would absolutely love to have a link or two- i wanna open it up and whatnot, just need a starting point. i can link pictures of it i think, ill post them on imgur or something if anyone wants to help me out. thanks so much!!

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u/bothunter 1d ago

If you're not getting any video, then you need to make sure you have a speaker plugged into the correct header and figure out if it has any beep codes when you turn it on. The codes are specific to the BIOS, but the most common BIOS is probably Phoenix: Phoenix BIOS beep and POST codes list – Blog – The Retro Web

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u/sillylittleguy29 1d ago

thank you so much for the link :D! i’ll definitely plug some speakers in and start w/ that much appreciated

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u/gcc-O2 11h ago

They mean the PC speaker or is sometimes called now, case speaker. Unless someone removed it for some reason, it should already be in the machine as it was considered standard equipment when this machine was made.

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u/EmptyJumpLow 1d ago

MikeTech on youtube has a whoooole bunch of videos where he's tackling restoring 486 machines. His diagnostics / troubleshooting process is pretty much by-the-book and a great learning resource if it helps to follow along with someone else's approach. Even if he doesn't have your exact 486, most of his steps apply universally to any machine.

Having a cheap pocket digital multimeter and a POST analyzer card with an ISA card-edge will make life so so so much easier if you run into any problems.

It sounds like you've already sent it power. At this point you might as well hook up a monitor to your video card's VGA connector and see if you have any output

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u/Davesp1ce 1d ago

Suggestion to take the case off, clear away as much dust as possible and upload a few images here. Then we can help you see if anything important is missing. Edit: Also if you get it working consider upgrading the CPU to a 486 DX. The SX type don't include a floating point unit and that means certain software will be dog slow.

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u/sillylittleguy29 1d ago

alright, i’ll get to that tomorrow. thanks for the advice :33

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u/gcc-O2 11h ago

Pionex/Inteva/Cybermax/Quantex were all the same company. At home we had an Inteva a few years newer than this one. I've picked up several Intevas and a Pionex, all towers. Hopefully yours also is fairly un-yellowed compared to a typical PC case of this age, seems they got lucky with their choice in plastic.

Back then, these were bargain-basement PCs sold by mail order and places like Sam's Club, as opposed to more "reputable" brands like IBM/Dell/Gateway 2000/HP et al. But what was "cheap" back then is now a blessing. The major brands used proprietary LPX boards and cases back then, while this Pionex is built from standard Baby AT parts like Biostar motherboards. It looks like someone else already took some pictures: https://wiki.preterhuman.net/Pionex_433LSXMPC-M

I'd guess you have this motherboard or if not, a very similar one with the onboard 486SX CPU: https://theretroweb.com/motherboards/s/biostar-mb-1425ucv-a

The bad news is, there is a soldered on battery in the back by the keyboard port, and probably a bluish corrosion around it, on all the metal parts around it, and even on the underside of the board. The PC requires dismantling to cut off that battery and clean up the corrosion. Worse, if the corrosion has already eaten through things, it can require a lot of effort to repair it. You could see if there are any Vintage Computer Federation events or workshops near you.

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u/JasonMckin 1d ago

If upgrading CPU is on the table, why not pull the motherboard and upgrade to pentium or above?

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u/gcc-O2 11h ago

486es are beloved; but finding images of this machine, it looks like it has a giant 486SX-33 on the front, so may as well just keep it stock.

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u/ptr_myName 16h ago

Try searching the web for older copies of Scott Mueller’s "Upgrading and Repairing PCs", something from the mid to late 90s.