Amiga 2000 Faulty when mouse pulled in

[LordFire]

Hi,
This might sound strange. I have an Amiga 2000 which boots ok from FDD and HDD and keyboard works ok, but when I plug in the mouse the displayed image goes mono and shifts to the left and the mouse doesn't work. I've swapped out the both 8520 from a working Amiga 500. I've checked for dry solder joints etc. All with no joy.
Any pointers?
Thanks.

[mechy]

Hi,
This might sound strange. I have an Amiga 2000 which boots ok from FDD and HDD and keyboard works ok, but when I plug in the mouse the displayed image goes mono and shifts to the left and the mouse doesn't work. I've swapped out the both 8520 from a working Amiga 500. I've checked for dry solder joints etc. All with no joy.
Any pointers?
Thanks.

did you try another mouse?

mech

[save2600]

Never, ever heard of such a situation. Have you determined the cause to the symptom because you are plugging the mouse in AFTER the Amiga boots up?

If so, I'd ask what kind of mouse are you plugging in? An Amiga mouse would not affect the computer that way.

Sounds like you might have a short somewhere...

[LordFire]

I've tried 2 x original mice and an Amiga 600 vintage mouse. I found the pin outs for the mouse port and I've got a DB9 I'm going to plug in tonight and try some stuff. I suspect it's some thing to do with +5V.

[dougal]

Did you ever try and plug in a pc serial mouse? I think that can cause damage.

[LordFire]

No the last time I fired it up a week ago it was working. I wasn't aware of PC mice causing damage. But I had just used th Amiga mouse. I hooked up a multimeter to the +5V and only got 2.3. Not sure if i will see 5 when there is no load. Tomorrow night I'll hook it up to the Amiga 500 and see what I should get.

[dougal]

No the last time I fired it up a week ago it was working. I wasn't aware of PC mice causing damage. But I had just used th Amiga mouse. I hooked up a multimeter to the +5V and only got 2.3. Not sure if i will see 5 when there is no load. Tomorrow night I'll hook it up to the Amiga 500 and see what I should get.

Maybe the PSU is starting to fail

[mechy]

No the last time I fired it up a week ago it was working. I wasn't aware of PC mice causing damage. But I had just used th Amiga mouse. I hooked up a multimeter to the +5V and only got 2.3. Not sure if i will see 5 when there is no load. Tomorrow night I'll hook it up to the Amiga 500 and see what I should get.

Some A2000's had small plastic pads on the bottom of the motherboard to keep the pins on the mouse port from shorting to the case as i recall, some didn't. Maybe this is the case with yours.

Mech

[Arkhan]

^^^^ What he said.

[LordFire]

Ok, looks like the mouse port is powered from pin 12 on the power supply which is '+5V User'. With nothing connected it sits at 2.3V instead of 5V and once I plug the mouse in it drops to 1.65V. When I hook up another +5V cable to pin 12 everything seems to work ok. I opened up the power supply to find I think a non Amiga PS. The Tick wire pin14 wasn't even hooked up. It almost looks like a AT power supply fitted in to the original PS case. I desoldered wire 12 and hooked it up to the main +5V feed. All back together again and it is working all ok now.