Mice not recognized

[Castellen]

the arrow on the lock was pointing to the right on the computer and points to the left on my A4000 desktop.

On the A4000T the switch points 'right' for normal operation.  But it doesn't sound as though this is related to the problem.  If it was related, you'd also find the keyboard wasn't working.

As already mentioned, check the 2 x 40-way IDC cables between the main board and ports module.  I had similar issues with mine recently with intermittent mouse movement.  I thought it was dodgy cables, but new ones had the same issue.  When the ports module and cables were moved the problem went away.  Doesn't appear to be solder joint issues, I gave up looking after the problem had fixed itself.  I spend enough time repairing customers' Amigas without having to fix my own.

Check you have 5V on pin 7 of the mouse port.  On the A4000T this supply is protected by polyswitch fuse F160 on the main board, so you can check that you correctly have 5V on both sides of that.  Though this also supplies power to the keyboard.  If the mouse/joystick port 5V output gets a short circuit to ground, I've seen cases where an internal 5V_USER track between CN550 pin 4 and FB556 can go open circuit on the A4000T.  Which is a bit of bad design on C='s behalf, polyswitch fuses have a very slow activation time and high fault current can flow for up to a second before the fuse opens.

I've written a few notes on diagnosing issues with the A4000D mouse port here, the A4000T circuit is practically the same with the exception that the signals route through the ports module.

Not sure why the subject of bad CIAs always seem to arise on the subject of mouse movement issues, these have nothing to do with reading mouse quadrature data in any Amiga model.  Worst case, you might have a faulty shift register U541 on the A4000T main board.

Edit: Just remembered this old thread where I'd discussed the same issues.  Wow, I noticed I had a "not the CIA" rant there too, I'm obviously becoming cynical.

[Castellen]

the cursor still doesn't respond to a mouse click

In your initial post, you said the cursor wasn't moving.  Now you're saying it's a mouse click issue?  Which is it?  The diagnosis for each of these issues is totally different.

If it's a movement related issue, follow my previous post.

If it's a left click issue, measure on U550 pin 10.  If it doesn't go low when you left click, then it's probably a connectivity issue to the ports module - trace the connection through to pin 6 of the mouse port.

If U550 pin 10 does go low when you left click, then replace U550.

[Castellen]

Back in the day I seem to remember the US magazines and my local repair shop always talking about mice and blown CIAs. As in hotplugging/unplugging mice could blow a CIA and then the mouse port wouldn't work... Maybe  not?

Don't feel bad, it's surprising how often one bit of incorrect information ends up being repeated so much that it then becomes widely regarded as "factual".  It's not just due to forums and the internet; once upon a time a majority of the population actually believed that the Earth was flat and the Moon made of cheese.  But I digress....

I'm not sure how it's possible to damage any of the I/O from hot plugging joysticks and mice, unless you happened to be particularly unlucky with an electrostatic discharge.  But that generally won't make much difference if the computer is on or off.  The basic resistor-capacitor protection on the mouse/joy ports is far from brilliant, but should be mostly adequate unless something particularly bad or stupid happens.  Most of the time the CIAs or other parts get damaged due to someone plugging something into somewhere they shouldn't.  Such as when people plug Centronics printer cables into the A3000 external SCSI port which blows up the termination power supply.  Moral of the story: just because the connector is the same type, it doesn't mean it should be plugged in there.

Port damage can often occur when the outer metal shell of a D-range connector shorts certain male pins to the edge of the connector (ground).  For this reason, you'll note that most 9-pin mouse and joystick connectors have a plastic outer connector as opposed to the metal shell.  The main area of damage would be shorting the +5V line to ground.  It doesn't matter if the left/right button or quadrature lines get shorted to ground, as that's how they're normally driven anyway.