Right fader knob doesn't do nothing. No sound come out from my right speaker when I turn the right knob up

There is NO way to select channels to "Source"... The selections on this mixer are to send the channels to SOLO, Sub1-2 or Sub 3-4 and/or main L-R. You should have the bottom button for each channel punched down to L-R. NEVER connect ANYTHING other than an external effects unit to the INSERT jacks!!!! These jacks are combined output/input jacks with send and return on the same jack. Special insert cables are used for these. An external drum machine should be connected to a line input for one of the channels USING a TRS balanced cable. Page 28 of your user manual shows the block diagram and signal flow diagram. The trim control is the input gain control. Start with those say at 12 o'clock and advance the fader for the channel of interest...you should get signal at the main outs. MAKE SURE that the lines from the mixer to the amps are BALANCED TRS type cables... You cannot use unbalanced cables for this. The user manual explains balanced cables and what they look like. I just repaired one of these mixers that some foolish people plugged stuff into the MAIN INSERT jacks and blew out the driver that drives the MAIN insert which kills the input to the MAIN output drivers. There is one small chip between the AMAIN fader and the sub next to it and one has to remove every knob and take the unit all apart to get to it... It is a tiny surface mounted part the size of a matchhead with 8 leads... not for the faint of heart to repair. As a test of this part, you can plug a st of headphones into the RIGHT MAIN insert jack and drive audio into a channel... turn trim control up fully for the channel and the fader on full, and set the PAN control to 12 oclock and punch down the L-R button for that channel. You should hear the audio in ONLY the left ear... Now try the phones in the LEFT INSERT jack... you again should hear the audio in the left headphone only (these jacks are not stereo like the headphones). If you cannot hear anything, then likely somebody has blown that driver in your unit... It is painful and time consuming to repair this... there are hundreds of knobs to pull off and put back on... dozens of screws and cables and to get it all back together. Also make sure ALL of your interconnected equipment is powered from a SINGLE receptacle or power module. Read your user manual thoughroughly. You can get one online download if you need it.

If you look at the signal flow diagram in your user manual, you will see that while AUX 1 and 2 can be selected are PRE or POST fader, AUX 3 is POST fader only... this means that the channel faders control the AUX3 level as well as the aux out level. Make sure you use TRS balanced lines to your speakers and not TS cables.

I answered another post of this earlier. The AUX3 is strictly POST FADER... you MUST turn the channel sliding fader up to send signal to AUX 3. Also the AUX3 channel gain KNOB must be turned up. Also the AUX master gain KNOB must be turned up. Make sure your cablles are balanced TRS cables from the mixer to the powered speakers.

Did you have the same speakers you test with at the store? If not, that is the problem. This unit will generate 400 watts a side when used on 4 ohm speakers, and a little over 200 watts a side with 8 ohm speakers and about 120 watts a side with 16 ohm speakers. For mics, the trim controls will be between 3 o'clock and full right. You set these using the PFL button with loudess vocal such that the indicator does not reach into the clipping. Do this for each channel. ALWAYS use balanced lines where possible. Use of unbalanced cables input results in a 6 Db loss. You will want to run the channel and main faders normally in the 80% range, like between -5 and 0 for BEST signal to noise ratio. There are good videos on You tube about mixer setup. If the speakers were not the ones tested with, your speakers may be the problem... I HOPE they are NOT consumer stereo speakers as you will soon smoke them with this mixer... the consumer speakers are very inefficient and you won't get much sound before blowing them up. If you spent less than $300 for EACH EV speaker new, it is UNLIKELY they are suitable. The suitable ones I found for 12 inch are around $600 each...hopefully these are the ones you have. There are less expensive brands. Frankly, if you want more sound, especially bass, I would go up to 15 inch speakers. These are probably the lowest end price wise to consider: http://www.musiciansfriend.com/pro-audio/behringer-b215xl-15-1000w-passive-pa-speaker Shop around, but stay with PA rated pro speakers as consumer ones just won't take it and eventually fail when used with these amps. ALSO be very careful if you use 1/4 inch speaker plugs as the SLEEVE of the A channel of this amp is the HOT, not the TIP of the jack... short the sleeve to something grounded and it is goodbye amp.

NEVER, NEVER put contact cleaner into the faders!!! It removes the lube and the faders will be damaged in short order. Try using CRC226 available at Home Depot in the electrical dept. Use ONLY the CRC226 as there are other CRC products that are not applicable. Squirt some in the center of the slots... not too much and work the sliders... if they improve try a little more... If they are still bad, replace the sliders... it is a MISERABLE job involing removing mass number of knobs, screws, etc... and then getting/finding the replacement fader control. Usually I get them from Digikey.com or Mouser.com and sometimes the actuator tab has to be trimmed to length with tin snips so knob will be at right height. The fader must have the same resistance and TAPER as the original as well as mounting tabs.

I HOPE you know that the monitor send jacks are NOT powered. You MUST use either powered monitors or an external amp for these to drive speakers. Assuming you have done that, you have to turn up one or both of the monitor knobs for each channel you wish to send to the monitors at the desired level. Then you advance the monitor faders for the overall monitor level.

Bridge mode you use chan B (left connector on the back) using a SPECIALLY wired Speakon. The impedance of a speaker connected as such CANNOT be LESS than 8 ohms.

In the Main/Mon mode, the two amplifiers are separated in function. The monitor knobs for EACH channel input control the mix sent to Channel A which is for the monitor speakers. The Mon1 controls the level sent to Output A for the monitor speakers. Mon2 fader is NOT used.

The individual channel faders control the main mix and the Main fader controls the level sent to Output B which goes to the main speakers.

There can be any number of reasons for this problem - solve it diagnostically by starting with something that you know is working and work through systematically to the other end.

1. Test a microphone on a separate amp to make sure it works okay. Check amp and speakers working. Check that all output cables from mixer to amp are working by testing separately.
2. Plug microphone into a channel on mixer. Also plug in headphones and turn headphone volume control up.
3. Make sure input sensitivity knob is turned up a bit (say half way) and main output faders (yellow) are up.
4. Check that channel is turned on (little button just above the channel fader- needs to be pressed down)
5. press pfl (pre-fade listen) button (next to button to switch channel on)- do you get any sound on main output or headphones or any indicator lights on mixer to show signal is getting that far (eitehr the individual channel metering lights or the main ones in the central section)?
6. turn off pfl - make sure channel fader (slider) is up - normal position is ) - about 3/4 of way up. Check lights again on individual channel and main output section - any signs?
7. Is the sub mix button for the channel pressed down - in which case you will need to bring sub mix (red) output faders up as well as main faders.
8. If you have got signs of signal on the individual channel but not main see if the channel has been routed somewhere odd (like a subgroup of channels).
9. Plug a working amp and speakers into one of the auxiliary outputs and use the relevant auxiliary send knob (on each channel just above the faders and pfl switches) to pan some signal to that auxiliary out - do you get anything? There is also a headphone socket for listening to the auxiliary channels (with a selector switch /knob to determine which one - make sure it is in the right position) try listening to the auxiliary output with headphones - anything? If yes the problem lies in the main output section.
10. Check that there is not a jack plug in the insert socket (to route signal through an external effects unit) without a matching return jack being plugged in - if appropriate is relevant effects unit switched on and correctly set up - if unsure remove the insert plug to take it out of the system.
11. Make sure any mute buttons are not switched in on main outputs.

You can download a full user manual here http://www.allen-heath.com/gl/gl2400

http://www.behringer.com/EN/downloads/pdf/1622FX_P0557_M_EN.pdf
there is the manual
But to actually answer some questions for you as well.
1. How do I connect it to my monitors?
Out of the back of the console there is a Main Out : Left and Right. there are two sets, one is XLR, second is 1/4 in. Run those to Powered Speakers and Voila.
Note: If you are using unpowered speakers then you will need a poweramp to run speakers.
2. and 3. first make sure your fader is all the way down
Once you plug in your microphone the top white knob is your gain preamp actually turning your voice going into the board up.
Second set your Main Mix fader: far right faders to 0. Then, the channel your microphone is on bring up the fader and you should start hearing some of your vocal through the monitors.
4th. At the Top right there are two sets of stereo ins (RCA) all you need is a 1/8 in to RCA cable coming out of the Headphone/Line Out of your computer.
Good Luck, Cody J.

The MON faders ONLY control the output to the MON L and MON R jacks, NOT the split use of MAIN/MON outputs. You MIGHT try varying the MONO fader and see if it varies the MON part of the split output.
Best to use the unit as MAIN L and R to main speakers and use a stereo amp or POWERED monitors driven from the MON L and R jacks. With this, the MON faders will control your monitors as you would like them to.
ALSO make sure ALL equipment connected together is powered from teh same recepacle power system. Powering interconnected equipment from receptacles at opposite ends of the room is asking for damage due to ground bounce and faults.
PLEASE read my tip on here about a HAZARD of speaker polarity if you use Speakon to 1/4 inch cables.