386DX-40 board, keyboard error, no lights to keyboard \ VOGONS

386DX-40 board, keyboard error, no lights to keyboard

Topic actions

Post a reply

First post, by DaveJustDave

Posted on 2020-12-14, 05:26

DaveJustDave Offline

Rank Member

Rank: Member
Posts: 338
Joined: 2013-10-03, 04:00

So this thing was JUST working. I was handling it a bit, and now it's acting up.

Tried different keyboards (which all worked on another machine, so I don't think its the kb fuse)

The joints on the connector look OK, no corrosion on this board, the battery was cut out a long time ago.

Checking 5V on the connector i get a really low reading, like 0.068v.

I am thinking it's a cap issue, otherwise it would read 0.00v?

Anyone have any insight? Thanks in advance!

I have no clue what I'm doing! If you want to watch me fumble through all my retro projects, you can watch here: https://www.youtube.com/user/MrDavejustdave

Reply 1 of 4, by majestyk

Posted on 2020-12-14, 06:48

majestyk Offline

Rank Oldbie

Rank: Oldbie
Posts: 1352
Joined: 2020-12-04, 09:13

I would check the 5V at both ends of the keyboard-fuse first. If it´s near 0V at both ends, check all 5V terminals at the AT (PSU) connector .
If there´s also 0V - does the PSU start up? Is the fan spinning? If not (and if the PSU is o.k.), there might be a shorted tantalum capacitor on the mainboard.

Reply 2 of 4, by sf78

Posted on 2020-12-14, 13:28

sf78 Offline

Rank Oldbie

Rank: Oldbie
Posts: 817
Joined: 2014-10-16, 15:05
Location: Finland

You can measure the tantalums (C11 and alike) while it's running to see if they work.

Reply 3 of 4, by DaveJustDave

Posted on 2020-12-22, 04:38

DaveJustDave Offline

Rank Member

Rank: Member
Posts: 338
Joined: 2013-10-03, 04:00

majestyk wrote on 2020-12-14, 06:48:

I would check the 5V at both ends of the keyboard-fuse first. If it´s near 0V at both ends, check all 5V terminals at the AT (PSU) connector .
If there´s also 0V - does the PSU start up? Is the fan spinning? If not (and if the PSU is o.k.), there might be a shorted tantalum capacitor on the mainboard.

I ended up following the 5V line, not very far. there was a fuse F1 that had no continuity. I jumped it and voila it works now. Probably not a long term fix though.

I have no clue what I'm doing! If you want to watch me fumble through all my retro projects, you can watch here: https://www.youtube.com/user/MrDavejustdave

Reply 4 of 4, by Deksor

Posted on 2020-12-22, 11:46

Deksor Offline

Rank l33t

Rank: l33t
Posts: 3388
Joined: 2016-06-07, 14:37

DaveJustDave wrote on 2020-12-22, 04:38:

I ended up following the 5V line, not very far. there was a fuse F1 that had no continuity. I jumped it and voila it works now. Probably not a long term fix though.

Nice. Maybe it just died due to static electricity ?

I have found your motherboard here
http://www.win3x.org/uh19/motherboard/show/1159

Would you like to upload a nice photo of it so we can add it ?
Can you dump your bios as well ?

I noticed at least one mistake that have been made by Microhouse : they indicate that this board has a ps/2 connector even though it doesn't

Trying to identify old hardware ? Visit The retro web - Project's thread The Retro Web project - a stason.org/TH99 alternative

Go to top of page Go to top of page

Back to General Old Hardware

Main menu

Common searches