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Problems with detecting keyboard on socket 7 motherboard

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First post, by ksiumaxx

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Hi. I have a PCPartner MB520NH motherboard which I would really want to use for my dos pc, but it's not detecting any keyboard I try. Din5, PS2->Din5 adapter failed, even tho all of the keyboards I tried are working, and get detected on other systems. When I boot the pc, lights on the keyboard don't flash once like they should, and it shows on the screen Keyboard error or no keyboard present. I saw this Keyboard error or no keyboard present post where they mentioned about a keylock jumper on the board, but I couldn't find any mention about it in the manual. The also mentioned about a keyboard fuse, which should be somewhere near the keyboard connector, but I wasn't able to locate it.
And I also have a question, which I couldn't find answer for even tho it could make using this motherboard much easier for me. If I would be able to make keyboards work again, could it be possible to replace Din5 connector with PS/2? I know I can just use a simple adapter, but adapters like that are not using any electronics, only wires so it should be doable.

Here you can find a manual and some specification about the motherboard: https://theretroweb.com/motherboards/s/pcpart … 20-03#downloads

Reply 1 of 21, by bogdanpaulb

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You can check with a multi meter the presence of +5v on the DIN5 connector on the selected pin.
The location of the KB lock connector it's in the manual, and is shown in the second picture.

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Reply 3 of 21, by bogdanpaulb

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Can you confirm: motherboard was turned on, multimeter was set on continuous voltage (e.g. 20v dc) and you used ground for the second lead of the multimeter ?

Reply 4 of 21, by Repo Man11

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When looking at the back of the motherboard you ought to be able to follow the trace from the DIN connector to the keyboard fuse. I have a PCChips M520 where the issue was a bad solder joint on the keyboard fuse and the solder joints for the DIN connector were cracked.

"I'd rather be rich than stupid" - Jack Handey

Reply 5 of 21, by ksiumaxx

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bogdanpaulb wrote on 2023-04-25, 15:35:

Can you confirm: motherboard was turned on, multimeter was set on continuous voltage (e.g. 20v dc) and you used ground for the second lead of the multimeter ?

Yes

Reply 6 of 21, by bogdanpaulb

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ksiumaxx wrote on 2023-04-25, 16:27:
bogdanpaulb wrote on 2023-04-25, 15:35:

Can you confirm: motherboard was turned on, multimeter was set on continuous voltage (e.g. 20v dc) and you used ground for the second lead of the multimeter ?

Yes

Can you post a picture with the area from the first picture (DIN5 connector area) front and back of your motherboard ?

Reply 7 of 21, by ksiumaxx

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bogdanpaulb wrote on 2023-04-25, 16:32:
ksiumaxx wrote on 2023-04-25, 16:27:
bogdanpaulb wrote on 2023-04-25, 15:35:

Can you confirm: motherboard was turned on, multimeter was set on continuous voltage (e.g. 20v dc) and you used ground for the second lead of the multimeter ?

Yes

Can you post a picture with the area from the first picture (DIN5 connector area) front and back of your motherboard ?

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Reply 8 of 21, by bogdanpaulb

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With power on, check with a multimeter the presence of 5v dc at all the points marked, careful not to short anything.

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Reply 9 of 21, by ksiumaxx

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So yeah my multimetemer wasn't in the correct mode. The Din connector isn't getting 5V on any of the pins, and the ones you marked got:
1. 5.10V
2. 5.10V
3. 5.11V
4. Top one got 5.10V and bottom got 0.69V

Reply 10 of 21, by bogdanpaulb

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Again, just to be sure, what was the voltage on the pins of the 'black' component ? Because you gave 2 values for nr.4.

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Last edited by bogdanpaulb on 2023-04-25, 18:04. Edited 1 time in total.

Reply 11 of 21, by ksiumaxx

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bogdanpaulb wrote on 2023-04-25, 17:56:

Again, just to be sure, what was the voltage on that pin of the 'black' component ? Because you gave 2 values for nr.4.

Becouse you marked 2 sides of the black thing before. The one you marked now got 5.10V

Reply 18 of 21, by bogdanpaulb

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Then search on the scrap/dead ones for a fuse and replace it ( the black component ). You should be able to find it in the same area of the motherboard, just post some pictures of what you found so you will not use a ferrite bead instead (they look very similar, the other 'black' component with pins 1 and 2).

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