Hello.
I just bought 5 vintage 486 mainboards, I got them cheap and I wanted to repair the damaged ones.
Some have obvious damage but I have no idea on the extent of the damage.
Some don't seem to be recognizable so I have no idea what jumpers I need to set to set up the testing cpu.
Here's the motherboards.
Tips in how to safely test them?
Safely test them? Damn, well I guess balancing on a tightrope over a live volcano while powering them up is out then. But anyway, basics first, check all power lines to ground for shorts.
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.
BitWrangler wrote on 2023-03-22, 16:30:Safely test them? Damn, well I guess balancing on a tightrope over a live volcano while powering them up is out then. But anyway, basics first, check all power lines to ground for shorts.
Yeah.
While it's not obvious by the photos (thanks Vogons for 5 photos limit), I've checked some of the boards that I've identified.
I noticed that some of the corroded boards, the acid has affected small traces on the other side of the mainboard (but the other traces are intact) while others have many rusted components or many missing capacitors/resistors/diodes.
The first one in the pic has a corroded big trace from the psu connector (486dx motherboard).
The second (496 386dx opti ver 1.1, a 386 motherboard) had many traces damaged (green gunk and oxidated ISA slots) by the Ni-Cd varta battery that was still on the board when I opened the package.
I have little hope on that being repairable.
Another socket 3 motherboard seems to have a badly soldered capacitor (seems a bad attempt to replace it) and signs of amateur soldering of a ni mh battery (it had leaked and was removed before i bought it) when the board already had a cr 2032 battery holder.
The one that did this sloppy work didn't even check that there was no circuitry to recharge the battery so it was left there until it leaked.
Only one seems 100% intact.
It seems to be a 486 dx with VESA motherboard, the settings on the board say "JPX 25-33-50 cpu clock" so i assume it may only support the first 486dx generation (need help to see if i can place a more powerful cpu on it), it seems intact as the board only had an empty cr 2032 holder, I've throughly checked it, no corrosion, got lucky on this one.
The other has minor corrosion signs near the battery traces (came clean with little effort) , only the cosmetic paint has worn off, but it appears a strange motherboard with no manual found online.
1st gen boards haven't got a lot to set usually, if they have a can oscillator, there's no FSB to adjust other than swapping that out. CPU setting is just between SX and DX, typically a 4 pin, where middle 2 shorted for SX, and 1-2, 3-4 for DX
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.
Luke4838P wrote on 2023-03-22, 16:13:Hello. I just bought 5 vintage 486 mainboards, I got them cheap and I wanted to repair the damaged ones. Some have obvious damag […]
Hello.
I just bought 5 vintage 486 mainboards, I got them cheap and I wanted to repair the damaged ones.
Some have obvious damage but I have no idea on the extent of the damage.
Some don't seem to be recognizable so I have no idea what jumpers I need to set to set up the testing cpu.
Here's the motherboards.
Tips in how to safely test them?
Hello,
Sorry, but.... those pictures. Do you want us to get blind?
The last one is 386 board by the way.
Pics are not great. Third one down doesnt appear to have a lot of damage though.
P1: Packard Bell - 233 MMX, Voodoo1, 64 MB, ALS100+
P2-V2: Dell Dimension - 400 Mhz, Voodoo2, 256 MB
P!!! Custom: 1 Ghz, GeForce2 Pro/64MB, 384 MB
Luke4838P wrote on 2023-03-22, 21:28:Only one seems 100% intact.
It seems to be a 486 dx with VESA motherboard, the settings on the board say "JPX 25-33-50 cpu clock" so i assume it may only support the first 486dx generation (need help to see if i can place a more powerful cpu on it), it seems intact as the board only had an empty cr 2032 holder, I've throughly checked it, no corrosion, got lucky on this one.
They probably will work with a 486DX2-66 CPU anyway (a nice fit since it was the last top-of-the-line 486 CPU before the Pentium was released).
The BIOS may mis-detect the bus speed and de-tune the system. I have an ISA-only, pre-486DX2 board where the AMI boot process runs on the slow side, and the memory test tick sound is on the deep side, but once it POSTs it's fast if you've manually configured things in Setup.
CoffeeOne wrote on 2023-03-22, 22:48:Hello, Sorry, but.... those pictures. Do you want us to get blind? The last one is 386 board by the way. […]
Luke4838P wrote on 2023-03-22, 16:13:Hello. I just bought 5 vintage 486 mainboards, I got them cheap and I wanted to repair the damaged ones. Some have obvious damag […]
Hello.
I just bought 5 vintage 486 mainboards, I got them cheap and I wanted to repair the damaged ones.
Some have obvious damage but I have no idea on the extent of the damage.
Some don't seem to be recognizable so I have no idea what jumpers I need to set to set up the testing cpu.
Here's the motherboards.
Tips in how to safely test them?Hello,
Sorry, but.... those pictures. Do you want us to get blind?
The last one is 386 board by the way.
drosse1meyer wrote on 2023-03-23, 00:18:Pics are not great. Third one down doesnt appear to have a lot of damage though.
Sorry, but i had to shrink some down as they were 25-30 mb of size, to reduce them to a 5 mb limit the quality had to go down, i uploaded others that let's hope are more clear.
jakethompson1 wrote on 2023-03-23, 01:33:They probably will work with a 486DX2-66 CPU anyway (a nice fit since it was the last top-of-the-line 486 CPU before the Pentium was released).
The BIOS may mis-detect the bus speed and de-tune the system. I have an ISA-only, pre-486DX2 board where the AMI boot process runs on the slow side, and the memory test tick sound is on the deep side, but once it POSTs it's fast if you've manually configured things in Setup.
The 486DX2 would be fine then?
I can use the SX for testing but some have no manuals.
Luke4838P wrote on 2023-03-22, 21:28:[...]
It seems to be a 486 dx with VESA motherboard, the settings on the board say "JPX 25-33-50 cpu clock" so i assume it may only support the first 486dx generation (need help to see if i can place a more powerful cpu on it)
On the contrary, 1st gen would probably have 16 and 20MHz as well.
Consider that this is the external CPU clock - what we later called FSB - and no 486 was specced to run faster than 50MHz - even the fastest So3 CPUs (5x86-133) only ran at 33MHz externally. All that's missing here is 40MHz, but that's a speed not supported by Intel, so it might just be focused on Intel CPUs.
Of course it would need jumpers to support WB cache, 3V/3.45V and other things for later CPUs, but purely the bus speeds aren't an issue.
Is this the AOpen (blue) Socket 2 board with SiS 85C461 chipset? If so it is an old one: no voltage regulator, no support for advanced caching features and the chipset is a hybrid 386/486 one...
I can't find the exact AOpen model number (don't think it's in TheRetroWeb), but the few settings appear excellently documented, so not a huge issue.
dionb wrote on 2023-03-23, 11:58:On the contrary, 1st gen would probably have 16 and 20MHz as well. […]
Luke4838P wrote on 2023-03-22, 21:28:[...]
It seems to be a 486 dx with VESA motherboard, the settings on the board say "JPX 25-33-50 cpu clock" so i assume it may only support the first 486dx generation (need help to see if i can place a more powerful cpu on it)
On the contrary, 1st gen would probably have 16 and 20MHz as well.
Consider that this is the external CPU clock - what we later called FSB - and no 486 was specced to run faster than 50MHz - even the fastest So3 CPUs (5x86-133) only ran at 33MHz externally. All that's missing here is 40MHz, but that's a speed not supported by Intel, so it might just be focused on Intel CPUs.
Of course it would need jumpers to support WB cache, 3V/3.45V and other things for later CPUs, but purely the bus speeds aren't an issue.
Is this the AOpen (blue) Socket 2 board with SiS 85C461 chipset? If so it is an old one: no voltage regulator, no support for advanced caching features and the chipset is a hybrid 386/486 one...
I can't find the exact AOpen model number (don't think it's in TheRetroWeb), but the few settings appear excellently documented, so not a huge issue.
Well, if that's the case I can try to test it with the 486 dx2 66.
Anyway, I've moved onto the 386 mainboard, scrubbing with a toothbrush and contact cleaner resulted in revealing that the two traces under the mainboard, that lead from a chip to a ram slot seem still there, the copper is shiny and clear after removing the green, despite they looked bad.
I've removed and used a metal brush to clean the keyboard controller, and there was minor corrosion on a trace that was under it, cleaned without too much effort and the trace is intact despite the protective paint has come off.
However, two traces near the battery that lead to the keyboard connector seems to be interrupted and will most likely need to be restored.
How do I clean the isa slots from that green filth?
