Quote Originally Posted by gfevan View Post
I have seen that if I make a test strip switching ON/OFF every 5 seconds the enlarger, makes darker strip than leaving the enlarger always ON.
That is unusual - when there's a mismatch normally you get a lighter one because of the switch-on time of the lamp and/or stabiliser. What sort of timer are you using? If it's not a digital electronic one it's quite possibly out of calibration; maybe 5 seconds is really 5.5 for instance?