Flash i have a canon digital rebel xti, everything was working properly until i connected a additional lamp, after disconnecting my built in flash lamp would not pop up. how can i fix this problem?

Flash ready light on , but dont fire, xenon tube need replacement .

The built in flash's autopop up is not working

This is a problem known by Canon, you will have to have it serviced.

Be aware that the built in flash does not pop up automatically in all picture modes. Try it when in the different modes (on the mode dial) and see what I mean. Does it popo up when manually opened ?, (small button on front left hand side of the viewing pentaprism/flash housing.)

i am having the same problom try this i just found this ... http://www.fixya.com/support/t1021194-flash_not_working

Automatic settings are not useful in all conditions. The built in flash is not good over 20 ft. Under low light conditions, an external flash is better option, but it costs additional too. Remember that shooting under low light conditions is always a difficult task. By the way, I don't know about such common problem in Canon XTi

Flash will automatically pop out only in AUTO mode, if the camera needs some additional lightning. In manual modes, you should use the flash button located at the left down side of the flash compartment, to manually force the flash to pop up

The flash up switch is not working properly. It probably just needs to be disassembled and cleaned. About a $125 repair at most shops.
Hope this helps.
Wes Kauffman

I also own a Vivitar 285 that i used with my Canon F1 manual 35mm camera. Most older cameras before the advent of digital, had a hot shoe on top of the camera, or like in my case, the hot shoe went over the rewind knob. I also had to plug in a power cord from the 285 flash foot and the cameras PC connection in order for the flash to work on some other cameras. The Canon Rebel XTi has a TTL (through the lens) hot shoe usable with Canon's own EX flash units. You can buy a "hot shoe to PC connector" if the TTL camera hot shoe doesn't work, but be extremely careful, the only problem that exists with the older manual flash units was the trigger voltage is as high as 200+volts which would fry digital camera hot shoes. I tried my unit with a Wein flash trigger device on the PC cord of the flash and my Canon D60 with it's own flash. All shots were overexposed and washed out highlights.  Here's a copy of the hot-shoe review:h The EOS 400D's hot-shoe can be used with Canon and third party flashes (although sync only on most third party units). The hot-shoe is E-TTL II compatible. Compatible flashes include Speedlite 220EX, 380EX, 420EX, 430EX, 550EX, 580EX, Macro-Ring Lite, MR-14EX, Macro Twin Lite MT-24EX and Speedlite Transmitter ST-E2.  The Canon Rebel XTi doesn't have a PC socket to plug in a manual flash trigger cord which common sense tells me there is no provision to step up the voltage to trigger manual flashes - so my answer is this combination is not a good idea on a Canon Rebel XTi. Hope this helps.

With the flash in the up position and looking at the flash housing, there should be a small, metal hook. Make sure it's not bent or distorted. I should be straight and spring loaded all the way towards the front of the body. Check for freedom of movement also.