Revive Your Dead 386/486 Motherboard

Probably nothing more frustrating than thinking you have an incredible piece of history at your fingertips… gathering up all the parts needed to get it going only to find it won’t turn on!

You had big dreams of playing with an original 1989~1997 motherboard and CPU to complete a childhood reliving retro build! Depending on where you live, many of these have already been long since recycled. Some of these aren’t aging well and weren’t stored in the best conditions… but here’s the good news:

They’re RARELY unrepairable.

Unlike today’s modern boards filled with microscopic surface mounted devices that are incredibly hard to replace… older motherboards are quite serviceable and repairable without a ton of skill required.

The basics of testing your board:

  • Installing a basic ISA video card (8bit or 16bit) or possibly an ISA/VESA model.
  • Install a CPU and double check the jumpers with a manual online… Likely one from Stason or similar.
  • Connect an AT style power supply to P8 and P9 matching the two black grounds together (side by side).
  • Connect an AT format keyboard (or adapter to PS2) 
  • Plugged an infernal squeaker (Internal speaker) to the board to monitor for sound output?
  • Maybe you also add a controller card for IDE, Mouse & Floppy (not needed for testing) 
  • Attach a VGA monitor to your video card, throw the switch and…


  • Zero output to your monitor?
  • Blank screen… AT power supply comes on and abruptly shuts off?
  • Maybe your power supply just hums while the power button’s… freaking you out and making you think maybe something’s frying and you quickly shut the bugger off!
  • Or it fires up and just runs with no video output.

Your probably wondering… why won’t this thing turn on? If AT power supplies are “DUMB” compared to their ATX counterparts, why wouldn’t it at least run the fans and fire up the drives, regardless of the board condition?

That whole “dumb” thing isn’t completely true.

Most good AT power supplies have a Power_Good signal that runs through the real time clock and CPU and if there’s a bad ground or connection between the BIOS/CPU, it may not even spin fans. It may act like a dead power supply – but it might not be. Detailed info about how different power supplies work here.

Things that can cause this and troubleshooting steps:

  • First place – is the actual power supply good?
  • Do you have a bad ground somewhere?
  • Is the CPU correctly installed?
  • Have you re-seated the cache and bios chips and cleaned their contacts and sockets?
  • Tried the isopropyl wash technique?
  • Followed the Power_Good pin with a multi-meter checking continuity to each placeon the board?
  • Looked for bad capacitors, broken components, lose things etc?
  • Checked the video card’s capacitors, connection to the board, given IT a isopropyl bath? Cleaned it’s contacts really well too?
  • Have you had a battery leak? If so, have you repaired the traces and reflowed solder on components that went grey or green? Checked for cracked solder pads on the board itself? 
  • Reseated the ram or checked if you’ve got EDO RAM in a board that doesn’t support EDO? Tested non-parity RAM vs parity or one stick at a time?
  • Do you have a different CPU to test? Have you checked if the CPU is getting the correct voltage on those pins?
  • Have you cleared the CMOS/BIOS by using the clear jumper or by removing the clock battery (if it doesn’t have a Dallas RTC)? ** NOTE ** some boards will be unusable if you turn them on with the jumper set to “CLEAR”. If you’ve already done that AND you’re reading this… you can have a fresh chip flashed with a new BIOS or buy an EEPROM burner and do it yourself. Don’t throw it away though… someone (guys like me) will rescue those boards.

NOTE: Some Skills Required

If you choose to get into retro hardware or electronics in general… (welcome to the club!) you may have to learn a few new skills to properly diagnose and repair your machines. If you were looking for “Plug in and play” virtual machines and emulation are probably your best friend.

Still wanting to do the REAL hardware thing?
Here’s a list of things you’ll want to learn to troubleshoot and maintain your machine.

  • How to use a soldering iron – useful for fixing the lines on motherboards, replacing capacitors etc.
  • How to use a multi-meter to check continuity (connection between two places) and voltage levels
  • What IRQ’s are, which are already assigned on your board and which are still available.
  • How to install Windows and Dos from scratch, basic BIOS settings (the software built into your motherboard chips)
  • How to read a motherboard manual and set jumpers
  • How to clean a floppy disk drive properly for maximum lifespan

There’s a saying I read once on the Vogons forums where someone said “It’s not really a true 486 if it doesn’t fight you a little” and it’s probably true. Can’t remember who said it but happy to credit the writer if I find out who it was.

That said, start by checking all these things. It’s pretty rare that a machine with all these things looked at isn’t going to fire with a basic setup.