#Dumb, and …..
6 messages in this thread
Help!
By mistake, I plugged a PC serial trackball into the mouse port and now have
lost the mouse functions on my A2500 (Rev 6.2) – I'm well aware that that will
blow out the chip controlling the mouse.
My questions:
What chips need replacing?
Are they soldered in or can they be pulled and replaced?
Where can I get them?
As a side note, the reason I had a PC trackball around was because my old
MicroSpeed trackball was getting very rough. At a discount office supply I saw
an exact same model PC Trackball and bought it. I changed the ball and all the
rollers over to my Amiga model and had essentially a new trackball except for
the circuit board.
THAT worked fine – but I had both trackballs and their cords hanging around and
I, of course, had to plug the PC model in without thinking.
Moral: After changing the guts, get rid of the PC.
Thanks in advance.
Stew
Stew Bloemer // AMIGA
\X/ on AUTOPILOT
Stew,
There's a fuse that provides power to the mice ports on the A2500s. That could
well be blown. It's a pico fuse (about the size of a standard resistor)
located just inside the case near to the mice ports.
If you have a volt meter and a steady hand, you can measure the mouse voltage
(or lack thereof) right at the connector. Pin 7 is +5 volts, pin 8 is ground.
Good luck, Bruce
I saw enough of those fuses go to inspire me to make a test jig for the
mouse port. Just an LED and 200 ohm resistor wired to a DB-9, but it
covers for those of us without steady hands. 🙂
-Jim
MOS via Autopilot & Amiga
Sure, that should do it just fine.
Bruce,
Thanks much for the information; it was a winner. I found the fuse by the
socket (marked F1) and it was open. Didn't have a replacement so soldered a
shunt acrossed the fuse and VERY carefully plugged in the correct trackball
this time. It worked!
You saved me a lot of hassle because I wouldn't have looked for a fuse, and it
doesn't show in my A2500 manual schematic.
Thanks,
Stew
Stew Bloemer // AMIGA
\X/ on AUTOPILOT
Stew,
Well, that's OK for now but next time you'll melt traces !! I, too, didn't
have a fuse handy so I used a resistor (47 ohms, I think). This will limit the
maximum current to 100mA during a short but still not drop much voltage when
using most mice and trackballs.
The best solution is something called a re-settable fuse. It's a device with
low resistance until it gets hot, as it would during a short. It then goes to
a high resistance and stays there until the short is removed. Perfect.
Bruce