When my phantom power is turned on . my condensing mic isnt working . at first i thought it was my mic . but then i got a new one and it still isnt working . what is the problem

Ramesh - Just a quick thought (may be way off beam..) dynamic or condenser mic's ? If condenser - did you use the phantom power switch? (right next to the main 'on' switch around the back)

Don't know what you are saying. Phantom power is only used for Condenser mics and a few DI boxes. Make sure you ONLY use TRS or XLR cables into ANY/ALL inputs when using Phantom power. Please describe what you mean by :some channels decide to come". ONLY change Phantom power when system is off as you will get loud noise often by switching phantom while live.

There is really no way for a condenser mic to damage the board UNLESS you break the ground and get a static discharge into the input. That can happen with any microphone and has NOTHING to do with the phantom being on or off. As phantom power goes on and off slight bias at the input preamps can make amps non-linear causing the raspy sound you heard. The Phantom LED means NOTHING as it shows the state of the phantom switch by connecting a 12 volt source through a resistor to the LED... It shows NOTHING regarding the state of the 48 volt supply. Each input circuit has two 6.8Kohm resistors to the swinger of the phantom switch 2nd pole that either grounds those or connects them to a filtered 48 volt source. As long as you don't have a static buildup there is NO need to turn phantom power on or off while connecting a condenser microphone. At each input when using the XLR jacks are two per side 470pf capacitors for RF bypass. For the XLR's there is a 10Kohm between the signal lines and two series 10mfd/50 volt caps in series of each input to block the DC, when using phantom power, from reaching the preamp stage. These caps have to charge and discharge when changing the state of phantom power so you should AVOID having the main amps being driven while changing the state of any phantom power. Always have the fader(s) down and any monitors down to avoid a thump and also the non-linear raspy transition as the input caps charge/discharge. So fix the microphone... don't know what type you have, but DO check the cable (first) as ALL three conductors MUST be good for a condenser mic to work on phantom power. A ground leakage or noisy connection will cause your symptoms. Use a SHORT known good cable right at the board to test the mic. The 48 volts is applied through the two 6.8K resistors between both the signal lines to the shield of your XLR cable. The microphone picks off the 48 volts with a similar circuit.
Now let's cover a very important thing regarding system safety: ALL, and I do mean ALL interconnected equipment MUST be powered from the same source. Professionals run a power cord back to their mixer right alongside the snake. This is to avoid ground bounce damage due to bad building grounds or ground faults.

Sorry, but the Lexicon Alpha does NOT have Phantom power and you can't use a condenser mic with it without a Phantom power injector or preamp.
If you mean you have a Phantom power injector then it should be working. Do you have seperate mics for the two channels of the stereo? If you have only one mic, then only one side will record unless you set for mono recording and then dump the recording into stereo voa Cubase. I would recommend you get a small mixer... even a 4 channel one to use ahead of the Lexicon so you can mix and PAN your mics the way you want them. The recording and trying to control the panning in Cubase can be frustrating... The Lexicon really doesn't have anything built in to PAN the mic to the center when stereo recording. Small mixers are inexpensive and often you can find them used or in pawn shops for cheap.

Sorry, but the Alpha does NOT have Phantom power which IS required for a condenser mic.

You will either have to get a mic preamp that supplies phantom power or go to a dynamic type mic if you stay with the Lexicon Alppha.

Sorry, but the DI-100 can OPERATE on phantom power, not supply it. If you have a mixer that has phantom power then you have no need for the DI box. DI boxes are to convert unbalanced signals to balanced to send via XLR or TRS cables.

If you don't have a mixer that has built in Phantom power or a source of Phantom power, then you need a mic preamp that can supply the phantom power.

Here is an example device, but DO shop[ around as you should find some even less expensive. Make sure they have phantom power.

http://www.amazon.com/M-Audio-Audio-Budget-Microphone-Preamp/dp/B000CZ0RZG

I assume you are using CONDENSER microphones, as these are really the only ones that can use Phantom power. Also do NOT use any MONAURAL connections to MIC jacks while using Phantom power.

Sorry but... Very simply, you CANNOT use a condenser mic with the Alpha since it does not supply the required Phantom power for the mic. You must step up to another interface to use condenser mics. You can use dynamic mics with the Alpha or other audio sources. I use a Roland/Cakewalk UA25E interface with condenser mics and also the Lexicon Omega which does have Phantom power for the mics..

Make sure you have Phantom power turned on on the Lexicon... Oh,oh... it appears that the Alphs may NOT have phantom power which IS a REQUIREMENT for most condenser mics...

The Lexicon Omega does have this but apparently the Aplpha doesn't have it.

That leaves you with the choice of either getting a dynamic mic that doesn't need Phantom, or replacing the Alpha, OR using a preamp ahead of the mic before the Alpha...

Sorry, but those are the only solutions I see for you.

REMEMBER that condenser mics pick up everything and you cannot run them into a PA or they will feedback.

If it is brand new, it is likely "pilot error" as setting these up if you are unfamiliar with mixers can be frustrating.

There are several things that must be done to have a working system. Correct speaker cables are one and the setting of all the knobs are important...

DO NOT REPLACE FUSE. If any LED's are on, fuse is OK. If fuse blows, service the unit before replacing fuse to avoid further internal damage.

Make sure speaker cables are good.

Set the level control for the channel you are testing up AND you may need to press the "PAD" button to change the input gain. Turn up the master gain.

Depending on the source you are using, line or mic you may need to change the PAD button.

NOTE: This mixer does NOT have Phantom power and cannot be used with CONDENSER microphones requiring phantom power. You will get no audio from a condenser mic without phantom power. You must use dynamic mics with this mixer.