VOGONS

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

Topic actions

First post, by eax

Posted on 
User metadata
Rank Newbie
Rank
Newbie

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 
User metadata
Rank Newbie
Rank
Newbie

Problem solved 😀

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

schematic.png

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:

octek_hippo_com1.jpeg

Here's the quick fix:

octek_hippo_com2.jpeg

Maybe this is useful for someone else too

Reply 3 of 4, by devius

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie

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.

Reply 4 of 4, by Ter Roshak

Posted on 
User metadata
Rank Newbie
Rank
Newbie

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

Go to top of page Go to top of page
Back to General Old Hardware
Close window
Close window