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Need some help with a 286 computer of mine.

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First post, by Munwele

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Hello, not so long ago I've been given a 286 desktop PC. Upon receiving it, I opened it up to see if everything's okay with it.
Everything was okay, well, it looked like it.

When I turned it on, it turned right back off.
I turned it back on, turned right back off again.
TURNED IT ON AGAIN, POWER SUPPLY EXPLODED.

I dismantled the PSU and opened it up. I saw that a capacitor had blown up, no big deal, replace and fire the thing up.
Before you ask, yes, the capacitor that replaced the bad one is of correct capacitance and voltage 😀

*Fingers crossed*
Yaaaaayyy, machines POSTs but...
Keyboard's not working.

Now, the keyboard port on the motherboard is a 5-DIN one. I am pretty sure the PSU damaged a part of the motherboard when it decided to die on me like that.

I'll post some pictures of this PC later this evening, well, I'll try.

Reply 1 of 5, by kixs

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Check the area where the NiCD battery is located. It's usually near the keyboard connector and when it leaks it makes damage to that area - traces. But you'll have to check to see how it looks.

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Reply 2 of 5, by Munwele

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kixs wrote:

Check the area where the NiCD battery is located. It's usually near the keyboard connector and when it leaks it makes damage to that area - traces. But you'll have to check to see how it looks.

Hi, I've just checked the battery and it seems to be fine. Unfortunately, I cannot post pictures today 😒
But... I've tried turning it on again and this time, it worked.
It seems to be working intermittently.

Reply 3 of 5, by Jo22

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Are sure the psu is fine again ?
Please also check the diodes and the voltage regulators (pinouts of 79xx and 78xx are different).
Do you see any discoloured parts ? There must be a reason the cap failed (despite age).

Normally, a damaged psu tries to protect its terminal devices.
It's primary mosfet is very though and the regulating circuit also has protection measures..
So it's likely that some other parts of it ceased to function.
If you can, use your POST card and check the voltages and error codes if necessary.
Or use a dedicated psu tester.

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 4 of 5, by Munwele

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Jo22 wrote:
Are sure the psu is fine again ? Please also check the diodes and the voltage regulators (pinouts of 79xx and 78xx are differen […]
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Are sure the psu is fine again ?
Please also check the diodes and the voltage regulators (pinouts of 79xx and 78xx are different).
Do you see any discoloured parts ? There must be a reason the cap failed (despite age).

Normally, a damaged psu tries to protect its terminal devices.
It's primary mosfet is very though and the regulating circuit also has protection measures..
So it's likely that some other parts of it ceased to function.
If you can, use your POST card and check the voltages and error codes if necessary.
Or use a dedicated psu tester.

Thanks for your reply. I replaced the PSU, and the problem is still present. I'll check for error codes.

Reply 5 of 5, by Jo22

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Good luck! 😀
And watch out for a 7905! Some 286 mainboards generate their -5v line themselves..

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

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