odd reactio when I switch controllers

[Omnicef]

I have everything operating fine using a HP laptop and 2 595's. However the HP is not very stable, (Windows...yeah!). Switched to my Sony laptop and I get really wierd reactions. Lights don't work at some areas. In test mode turning one channel on and off a few times seems to turn off different combonations of channels at the other end. Noted that the sony did not have a ground prong on the plug. Ran a wire from the frame of the external PS for the 595's to the ground on the parallel port plug, combining the grounds on the pin. no luck. I know I must be missing something elementary or could the 2 laptops have that much difference in voltage output to not work? any ideas?

[Macrosill]

Could be a voltage issue. Or the parallel port setting. Or a ground issue. Check all of these things.

[daviddth]

Its not so much a ground as in earth, but a 0V link between the PC and the controller. Connect one or more of the ground pins in the parallel to the 0 volt of the 595 board.

If the voltage is an issue, as I have here, there is a way around that too. How are you powering the 595 board? i.e. from an old PC power supply etc?

[Anarchtica]

I would definitely go into the bios and change your parallel port setting to EPP mode and see if that fixes it. This is a simple step that could save you a lot of time troubleshooting the wrong things.

[Omnicef]

It was the parallel port issue. Did not have the regular selectins though in the setup menu. Had to try each one. All running and happy now. Thanks guys.

[Macrosill]

Which was the setting that worked?