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NEC ProSpeed 386SX doesn't work

A

alex_theman45

Member
Joined
Nov 15, 2013
Messages
24
Location
Florida
So I acquired a NEC ProSpeed 386SX Modular PC, and it doesn't seem to boot or make any signs of being alive. As such, I think that the capacitors are broken and or blown. I would like to get this repaired, so could someone point me in the right direction?
 
- Make sure the jumpers on the board are properly configured
- Remove and reseat the RAM and the expantion cards
- Look for the mainboard battery. If it is barrel shaped you need to remove it to prevent corrotion. If you see green-colored traces whose sourse is the battery then some damage on the board is already done. The metals that suffer from corrotion will have decreased conductivity and it might fatal on some occations.
- Next thing to check is the PSU. Having a voltage meter is useful to check if the voltages are close to what they intend to be or not.
- The capacitors on the board are the most frequently failing parts, especially those tantalum early boards tend to use, but usually when they fail, they fail opened and this should not prevent the board from booting. In the rare case that they fail shorted they can cause serious problems. They are usually a pain in the rear because they often have failed but visually look OK and you cannot test them without removing them from the board.
- The RAM is another part that can cause the board not to start if it is bad, incompatible with the board, or even inserted in the wrong bank
 
I would check the caps on the PSU, that thing has got to be 25-30 years old and the caps are well beyond their service life.

You can buy a replacement unit if you want. Newegg has one unit of dubious quality that may or may not work:

http://www.newegg.com/Product/Produ...&cm_re=AT_power_supply-_-17-338-010-_-Product

If the AT power supply isn't repairable by recapping it, I'd go the DIY route and transplant the AT power connector from the dead PSU to an ATX PSU with a -5v rail. I did this for one system and it worked really well. The only issue was having to modify the big power button to be able to short the power on wire on the ATX PSU.
 
Alex.
Try to find on the internet how to test an AT-powersupply.
Its easy.
Just connect the Power-on wire and put some power resistors at the output for balast the power unit.
So you can safely test the powersupply without the change to blow up yout M-board.

fi type in google
"test at power supply"
 
Any idea what is wrong with this "Power Block?"
0NUmnr0.jpg
 
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