A2000 bad mouse

[curtis]

Okay, I'm beginning to think I'm snake bit.

I got the CD-ROM in to install in my A2000.  Checks out okay.  Yay!

So, I'm putting everything back together employing cable management and wiring routing to keep things nice and neat.

Power up afterwards and suddenly the mouse is stuck in the upper left hand corner and only the right mouse button works!  HUH?!?!?!?!

So start stripping things down to make sure there's not a conflict anywhere.

Thylacine board, out!

GVP 030 combo board out!

Down to motherboard and nothing else.

Pop in a boot floppy and turn on the power.  Nothing!  NADA!!!!

Check the cpu and it's just sort of sitting there not making very good condition.  Suddenly remember using the larger pins from the expansions I'd plugged in there and realize some pins are probably not making contact.  Fortunately I have some spare sockets with the larger pins.  Install those and power up.

Computer boots up.  Yay.

However, the mouse is still stuck in the upper left corner and only the right button is working.

Fire up the PC and web search for probable causes.  Hmmm, says check the odd CIA chip.  

Okay, I've got several known good spares.  Swap BOTH out (just in case...).  Check contacts and legs for any bent or possible bad connections.  Looks good.

Power up.  SAME THING!!!

Mouse?  Swap mouse with known good.  No change.

Looking for suggestions, please!

Curtis

[curtis]

@ Orange, will check voltages when I get home.  Oh wait, "She Who Must Be Obeyed" has decreed we're going to to dinner tonight.  Guess I'll check it out when we get home...

@ Mike, I've had it down to just the mbo, what the heck, pull the motherboard out also!

@Nitro, no, the 2000 doesn't have a keyboard/mouse lockout.

[curtis]

Found the schematics for the mouse port and checked voltage.  5V line dead!

Next, find schematics to chase down the 5V line.

Oh drat!!!  There's a fuse in the line.  Fire up the computer, check one side of the fuse, nada!  Check the other side, 5V!

Grab a jumper wire with clips on the ends and bypass around the fuse.  Turn on, again.  Mouse moves perfectly!!!!

So, I'm thinking of just soldering a small, single strand of wire around the fuse, unless someone happens to know the value of the fuse link AND if they're readily available at Radio Shack.

Comments?

Curtis
Curtis

[curtis]

Mike, good point.  I have been noticing every time I touch a piece of metal near my workbench, the screen flickers!  Guess I'm building up quite a bit of a charge just walking around barefooted!

There's not a single mark on the stupid thing.  Just a green resistor looking critter.

Guess I'll dig through the internet and try to find the value.

As far as troubleshooting, I have to lay a lot of the credit on the people here who responded.  Sure makes things a lot easier when you have resources who have been there, done that around.  I just follow suggestions and go from there.

That fuse saved your a** one time, I'd try to replace it with another one.  Is there no markings on or near the fuse to indicate it's value?  Great job troubleshooting!

[curtis]

More info for those who are interested and may have to revisit this one day...

The fuse is a 4 amp pico fuse by Little Fuse.  Not sure on the series, but it's approximately 1/4" in size, approximately the siae of a 1/8W resistor.

Now to find a source.  Obviously, Radio Shack won't have it...

[curtis]

Well, I think I have it identifies, at Digikey I picked part number F3173CT-ND.

Heck, looking at the specs, there were several basically the same, so I took a stab and picked one with the right sizing and ampere rating.  On a 5 volt line, I really don't think there's much difference between a 125V and a 250V fuse!

Went ahead and ordered 10 to get the 4 cent price break AND to have a couple of spares, just in case...

So, should arrive in a few days.  Will replace then.

Also,if anyone else has this problem, you now have a couple of sources for fuses, either Digikey or you can give me a yell!

Now to somewhat reassemble this beast while I wait for the fuses to come in and start working on the next project.

I hope people who have been following this thread picked up some useful info and tips so you don't have to pull your hair out like I've done...

Curtis

[curtis]

Kind of figured that's what the voltage rating was.  Since the line is a 5V line, I'm pretty sure I'm okay with 125V rating!  

Got the fuses in yesterday.  Box really had me confused as to what it was until I opened it.

These things are TINY!  About the size of a 1.8 watt resistor.  The box was 8"X8"X1"!  Yeah!  There was more packing material than merchandise!  Heck, they could've just used a couple of pieces of light cardboard (like a cereal box) and shipped it in a plain envelope.

Anyway, will replace the fuse tomorrow and go from there.  Will probably just clip the leads on the old one and make a small curl on each end of the new one and solder it in like that.  Clip the excess lead and done.

Curtis