Amiga 1500 joystick issue.

[Amiga-fan]

Hi all,

I recently got an Amiga 1500, refurbished it all, but there is one slight problem remaining. The mouse works perfectly on port 1, but if I plug in a joystick, only the fire button works, but none of the directions do - the joystick works perfectly on port two and on both my A1200's though. I read somewhere there is a 5v chip that can cause this - can anyone direct me? The battery had leaked a bit (20 years in storage!) but this has been removed, the board was removed and cleaned including fitting a new CPU socket etc as well, but wondering if it has hit the joystick port 1 or the trace perhaps too. Thanks in advance.

[Daedalus]

The 5V supply has a fuse that is regularly blown, but this normally only affects mice. It's unlikely to be the 5V supply as joysticks don't normally use it. I would look at the area around the port, the resistor pack (RP200) and the multiplexer chip (U202) - I suspect one of those parts or the board around them is damaged.

[Amiga-fan]

Ahh, thanks for confirming that regarding the 5v.

I have been pointed in the direction of the CIA chips also - have been told I should swap these around and see if other symptoms appear and if so that indicates a faulty chip.

[solarmon]

The direction signals (M1V, M1H, M0V, M0H) ultimately goes to Denise, not the CIA chips.

[Daedalus]

Indeed, the only job the CIA chips have regarding the controller ports is the first fire button or left mouse button. Everything else is handled by Paula and Denise (or Lisa on AGA machines).

[Amiga-fan]

Thanks guys - managed to get a NOS Denise chip, so will see if that helps me out, if not Paula will be next!

[Daedalus]

Fair enough, though I should have made it clearer that the fault is much more likely to be the '157 chip or the resistor pack - I've never personally seen controller faults caused by a faulty Denise or Paula.