--- On Tue, 6/9/09, James Fraser <wheresthatistanbul-pcil...@yahoo.com> wrote:
> However, when I try to plug in
> a PS/2 version of that same ADB mouse, (not concurrently)
> the PS/2 mouse behaves from the get-go as though I'm holding
> down the mouse button when I haven't touched it. Yes,
> it could theoretically be behaving that way because of a bad
> port on the converter, but I can't help but think that if
> the port were bad, it wouldn't support mouse movement, which
> it *does* support just fine.
Tried the PS/2 mouse on a PC? Does the button make a 'click' you can hear and
feel when you press it? Do both buttons act the same when pressed?
Most mice these days use dome snap-action switches. They have a tiny metal dome
inside the switch. The dome has a small hole in its center so it acts like a
ring shaped spring.
The click sound and feel is from the dome snapping back and forth like the
bottom of an old metal oilcan's bottom.
After a whole lot of snaps, the dome spring cracks and often lays out flat so
it makes either constant or erratic contact.
The other main type of mouse button switch is the microswitch. These are a
rectangular plastic block with a tiny, rectangular button on top. They have a
thin, metal spring lever inside with a specially formed crease so it'll snap
back and forth between two contacts when the button is pressed. (Most of these
have a normally closed and a normally open contact, the NC contact isn't used
in mice.) The failure mode is similar to the dome type, after a few gazillion
(or less) snaps, part of the spring cracks then it just flaps around like a
cooked noodle.
The easiest fix is to replace the mouse. Another fix is to find another mouse
with a bad switch of the same type and transplant one of its good switches. In
extreme cases where you don't have a soldering iron but *do* have a pocket
knife and super glue you can pry apart the dome type switches and transplant
just the dome spring, then CAREFULLY use *very tiny* drops of super glue to put
the switch back together.
Yes, I've been in this very situation where I had to get a computer going and
luckily happened to have two mice with dead left buttons that used the same
type of switches. :)
I've also opened up microswitches and swapped parts, but they're harder to open
and have to be removed from the PCB to do it. (I would've loved to have seen a
scene like this on the new Battlestar Galactica series. Without being able to
just call up the fleet supply warehouse, it would've come down to saving and
cannibalizing the best bits from bad switches to keep things working.)
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