keyboard controller 8042 variant MEGATRENDS MEGA-KB-H-WP \ VOGONS

keyboard controller 8042 variant MEGATRENDS MEGA-KB-H-WP

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First post, by eax

Posted on 2017-01-10, 20:32

eax Offline

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Joined: 2016-12-30, 20:39
Location: Belgium

On a 486 mainboard I removed a leaky battery which was close to the keyboard connector. I seems to work but the keyboard does not work.
The visible traces are ok but I can't find any connection to the keyboard controller.

The 40 pin dip ic of which I assume it's the keyboard controller is labelled with:
MEGATRENDS
MEGA-KB-H-WP
I suspect this is a 8042 clone, I haven't found a datasheet for this part.

I compared with two other 486 mainboards with a 40 pin dip ics:
WINBOND W83C42 : key_data on pin 39 key_clock on pin 1
BESTKEY : key_data on pin 27 key_clock on pin 1

So the pinout seems to depend on the ROM mask of the 8042.

Does anyone have a mainboard that uses a MEGATRENDS MEGA-KB-H-WP and could beep the keyboard clock/data pins for me?

Reply 1 of 4, by eax

Posted on 2017-01-10, 22:07

eax Offline

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Joined: 2016-12-30, 20:39
Location: Belgium

Problem solved 😀

The best hint was this schematic in the winbond W83C42 datasheet:

The attachment schematic.png is no longer available

The MEGATRENDS MEGA-KB-H-WP uses the same configuration and a 7406 next to it.
Both copper traces for keyboard clock and data seem to be damaged, probably close to where the cmos battery was.

The mainboard is a octek hippo com EP40085R21-198 REV 2.1 with a Am486DX-40:

The attachment octek_hippo_com1.jpeg is no longer available

Here's the quick fix:

The attachment octek_hippo_com2.jpeg is no longer available

Maybe this is useful for someone else too

Reply 2 of 4, by Anonymous Coward

Posted on 2017-01-10, 22:22

Anonymous Coward Offline

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What a strange board. Why does it waste so many slots?

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

Reply 3 of 4, by devius

Posted on 2017-01-13, 18:39

devius Offline

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Location: Portugal

Probably because of the onboard IDE, floppy and I/O controllers. I guess they hadn't integrated these into any chipsets then, and the board is too small to have the necessary extra circuitry and keep all the slots.

Retro Coisas no YouTube

Reply 4 of 4, by Ter Roshak

Posted on 2018-09-01, 06:56

Ter Roshak Offline

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Do you still have the board and could you fetch me a bios dump?
That would be awesome ! 😁

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