Subject: PS/2 keyboard port broken by wrong adapter
To: Wim Vandeputte <>
From: Miles Nordin <carton@Ivy.NET>
List: port-alpha
Date: 05/18/1999 13:38:30
On Mon, 17 May 1999, Wim Vandeputte wrote:

> One of the causes I found was somebody using a serial -> ps/2 converter
> for his mouse, thus 'breaking' (blowing?) something inside the machine.
> Now, even with the mouse and converter removed and with a fresh keyboard
> and mouse, the system will just assume there is nothing hooked up thus
> booting with 'serial console' only, leaving a blank screen.

I fixed some worthless piece of Wintel refuse that had gotten into this
state with a fuse from Radio Shack.  It's poor owner had tried to plug a
wireless keyboard into it, using the wrong card-slotcover-cable, or using
the identical-looking completely unlabeled IrDA port instead of the PS/2
mouse port.  I forget what happened, but he blew the fuse.

The problem occurs because the +5V line to the keyboard is fused, and can
be shorted to ground by the wrong kind of adapter.

If you're experiencing a state change that survives unplugging the
machine, the fuse I spoke of is likely the culprit.  I don't have a
Multia, but the board I fixed had the fuse close to the keyboard
connector.  Fuses are easy to spot because (sometimes) they look like
fuses.  Also, they are labeled Fn, often along with a number of amps like:  

  F3 1A

If it's surface mount you might consider paying a shady electronics place
and telling them how to fix it.

Miles Nordin / 1-888-857-2723
555 Bryant Street PMB 182 / Palo Alto, CA 94301-1700