🚀 go-pugleaf

Christian Stieber <stieber@Informatik.TU-Muenchen.DE> said
in comp.sys.amiga.hardware on 26-Feb-97 14:33:58 -->
 CS> Pat Fish (fishp@sunyit.edu) wrote:

>>   What would cause the mouseport to stop reading the X-Y motion of the
>>   mouse?
>> I have verified that the mice are in working order.  It's the mouse port
>> that doesn't work.  The mouseport does however, detect when the
>> mouse-buttons are pressed.

 CS> Chances are the fuse is blown. Look for a small thing that looks like
 CS> a resistor, but doesn't have colors. It's probably located somewhere
 CS> near the mouseport, and might be labelled with F?. Just bridge it with
 CS> a piece of wire and see if this gets the mouse working again.

BE CAREFUL!  I've looked over both my A3000 and A500 schematics extensively over
the last couple of weeks and those "F?" parts most likely are NOT fuses.  On
both of my systems, these are filters to keep noise from getting in or out of
the computer through the pins.  They are a 3 wired device in which the center
pin is connected to ground.  Check the circuit BEFORE just shorting accross it. 
If the center pin is ground, then ONLY jumper the two end pins on the filter to
see if it starts working again.  Connecting either end to the center WILL kill
that data line by shorting it to ground.  This shouldn't damage anything, unless
it is the +5V power line, then you'd end up smoking a resistor somewhere else on
the board.

An easy way to test them is with an ohmmeter.  Each of the filters should
measure a dead-short between the end pins, and a fairly high resistance (if at
all) to the center pin from either end.  If it measures open between the end
pins or shorted to the center pin from either end, then it definitely is bad. 
Also, you should check the power line to the mouse port.  I had a resistor smoke
some, but couldn't trace it down until I checked it with the mouse plugged in. 
The resistor on the power line didn't burn and open completely, but raised it's
resistance.  Without the mouse plugged in, I had 5V at the mouse port, but only
about 2.5 to 3 volts with the mouse plugged in.  That explained my goofy mouse
operations, since 5V TTL circuits need at least 4.8 volts to work right all the
time!  I replaced the resistor and it works fine, now.

--
Daniel J. Andrea II  http://www.tfs.net/~dandrea  <dandrea@unix.tfs.net>
Amiga 3000 16F 2C, 1 gig HD, Iomega Zip, AmigaOS3.1, CV64, Stylus Color IIs
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And now...
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