I have a problem with my PIC burner. It detecting by P18pp, but Vdd & Vpp leds dnot changes, then I click Vdd/Vpp on/off buttons. Vpp(red) led is always ON. I use 74c14 instead 74hc14, is it my problem? they differ? see photo.
mmh. no picture visible here
“Vdd Enable” and “Vpp Enable” signals on 74C14 inputs are changes when you clicking Vdd/Vpp on/off buttons?
About 74c14 instead 74hc14 I don’t know, but think is another cause!
No, they dont changes. Vpp always enabled(then 74c14 are on their places).
May be you have another PC with LPT port,too.
my Pic burner module don’t working with my IBM Thinkpad computer, but it stable works with another - desktop PC.
Solution found 
I replace 74c14 with our Russian 555TL2 
. It works excellent!