The flash on my camera

Hi,
You might be shooting with a higher ISO or in settings where the D40 meter finds enough light and doesn't activate the flash.

Try changing the ISO to a lower one, like ISO 200 and take some test shots indoors, in a darkened room.

OR, you might have the mode dial set to "no flash". That's the crossed out lighting-bolt symbol. Just set it for P or another mode and you're back in business.

Hope this helps

It sounds like you're trying to use the SB-600 off camera, as a slave flash. While the SB-600 does indeed have slave capability, the D40 does not have the ability to function as a commander. Thus, the SB-600 is being triggered by the D40's pre-flash.

As stated above, the D40 does not function in commander mode. You can mount an SB-800 or SB-900 flash unit, which will function as a commander as well as a flash. Or you can mount an SU-800 commander unit.

Alternatively, you can switch the D40 to manual flash mode so as to eliminiate the preflash. However, you will then have to calculate the proper exposure yourself.

F-stop or lens flash rate

You can but with limitations;
Save me explaining,please read this http://forums.steves-digicams.com/nikon-dslr/137618-sb-25-d40-non-ttl-auto-mode.html

there is a sensor in there that tells the camera the flash is up you need to take it to a repair shop its not a at home thing

hai i think u told only sometime....
may b ur settings are not rit in the cam.

Ken Rockwell is the king of this type of request:
http://www.kenrockwell.com/nikon/d40.htm

no

Sounds like the external flash is being triggered by the pre-flash.

On the D40 set the flash mode to manual. On the F65 set the flash mode to Standard TTL.

I have also had the problem of flash not working on my Nikon D40. I found out the problem and I made a quick video to help those who are having this problem. Here's the link to the video: Hope this helps !

Nikon Flash Fix