I built this **broken link removed** programmer, and it doesn't work on my Laptop! But it works on my table computer! Why? Anyone now the answer?
Please help! Thx
it is quite possible that you may have damaged your parallel port. this is common with laptops. usually people unplug their printers from the parallel port while it is active. try to do something else with your parallel port (like connect a parallel port printer), if it doesnt work too then your port is damaged.
The control outputs on LPT (here, those coming out on pins 1 and 14 of LPT connector are used) may be open collectors so they cannot source the current needed to open the transistors - if it is so, the LEDs turn never ON. If it is so, try using some carefully chosen pullups.