Joystick Port

[Dagger]

I had a dead 1200(no display) so I have just purchased a motherboard from the common market. The replacement motherboard is all working apart from an apparent problem with the joystick port. Until I receive the board I don't know what the exact problem is, I just want to know if the port is dead etc can it be repaired. I am not to hot - clever when it comes to major repairs, I can swap chips cables etc but my soldering iron has a tip about the size of my finger . I was hoping that if any spares are required I could source them from the dead board. I just need to know where to start the interigation.
Many thanks in advance if anyone can help.

[rkauer]

Start by refluxing the solders on the joystick port.

[Dagger]

Ok. Thats good advice, thankyou

[Matt020]

Try swapping CIA chips from the other board, I beleive its the CIA's that control joystick/mouse ports?

[Toni Wilen]

You don't swap A1200 CIAs easily. They are surface mounted without sockets. Fortunately CIAs have nothing to do with most joystick or mouse functions.

First check possible broken connections, use multimeter to check connections between port pins and chip pins, check that there are no shorts to either ground or +5v (if one direction is stuck for example). Download schematics from eab file server.

Possible chip faults (A1200 only):

If joystick directions work in mouse port but not in joystick port (or vice versa): U34. Lisa is most likely ok. If both have 100% identical direction problem: U34 or Lisa (but highly unlikely).

If mouse left/joystick fire button does not work: CIA

If mouse second (or third) button does not work (or analog joystick directions): capacitors in POT lines or Paula.

[Dagger]

All I know so far is the mouse port works perfectly. Not sure whats wrong with the joystick port yet. Hopefully the board will turn up tomorrow.

[rkauer]

Then, again, check the solder in the joy port, then buzz the resistors in line with it to CIA.

A blew up resistor on those data lines is a very rare thing to appear. But you'll never know without trying.

But even if you can't find the defect, never throw the defective board away: sell it as defective or give it to one skilled Amiga here or on Amibay.

I'm good candidate!

[Dagger]

Ok. Well at the end of the day I will have a spare board. The other one has power going through but just gives a black display on the rf and composite

[rkauer]

Nothing on RGB, too? Chances are the CXA1145 bit the bullet.

[Dagger]

Will try the rgb over the weekend as I have found a lead. The replacement board has still not arrived yet

[Dagger]

I have had a a quick try of the replacement board when it arrived it does work fine apart the joystick port. The fire button works fine but there are no directional functions. It's a 2B board where the mouse part of the board can be completely disconected from the main part of the board. I have removed the bottom sheilding to make sure there are no shorts and the joystick port looks in good nick with good soldered joints. As none of the directions work does this suggest something bigger than just a dry joint etc?
The old board that I had has been tested on a monitor now but still displays a black screen the same as the rf and composite. Further test on this board shows that it does work fine. I can load games on it. If I fine tune the television I can just about see the disc moving on the boot screen.