QSC Audio Players & Recorders - Popular Questions, Answers, Tips & Manuals

The red clip lights on the QSC RMX2450 indicate that the amplifier is receiving a signal that is too strong and could cause distortion or damage to the speakers. The green lights indicate that the signal is within a safe range. When there is no input signal, the amplifier defaults to the red clip lights as a precautionary measure. Once a signal is received and it is within the safe range, the lights turn green. This is a normal behavior for this amplifier.

possible wrong speaker impedance

If you remove the grille and un bolt the speaker, remove the connectors on the speaker input and use a pp3 battery to test for movement of the speaker cone.

https://www.qsc.com/resource-files/productresources/spk/k.2/q_spk_k.2_usermanual.pdf https://www.youtube.com/watch?v=CJ2YBbSLWw0 https://www.manualagent.com/qsc/k10/owners-manual/page-102

You have a high power amplifier and the work you propose leaves no room for either error or compromise. If, as you suppose, the output is by complementary pair, the transistors must be matched pairs providing equal gain characteristics. Unless you have seen inside a complete amplifier of the type you are only guessing at the output stage(s) that could be by module or a multiple transistor output. There also might be other driver stage(s) sharing the same heat sink. The least you will need is a service manual and an internet search produced a number of results on the below link. https://www.google.co.uk/search?rlz=1C1CAFB_enGB673GB676&ei=PtG_W56NM6mIgAaYwaqIDg&q=qsc+mx1500a+service+manual&oq=qsc+MX+1500a+amplifier&gs_l=psy-ab.1.3.0i71k1l8.0.0.0.32505.0.0.0.0.0.0.0.0..0.0....0...1..64.psy-ab..0.0.0....0.D6yNqkAW5nw

When you buy anything used there is always the possibility that someone has messed around inside it. Are these two amps the same you bought? If they are you can open both of them up and see if anything has been changed. Again if they, are I suspect you will find that someone might have rigged it so the power switch is bypassed. Presumably the switch broke, the person either couldn't find a switch or just couldn't bother to get a new one! If they are the same model, then the one with the working switch should show you how it is wired correctly. Don't rewire the other model the same as your good one, till you have replaced the switch. As it could be a safety hazard. I would also advise not using the amp with no power off switch working, till it is replaced. Again due to safety concerns.

That system speaker is rated up to 450 watts.

Are you then saying you have no sound, yet the amp is on? If so, with the unit off, listen carefully to the top of the amp. When you first push the power button, you should hear one click, followed by another click, about 5-20 seconds later. I'm guessing you hear the first click, but not the second. Is that correct? If this is correct, and you are interested in having your QSC repaired, Please visit my website at audioserviceclinic.com. You may contact me there. Thank you.

The output of the mixer goes to the input opf the QSC rmx850.

Try a Google search, or contact QSC. They are still in business.

try this

You would have to replace them. If they are no longer available, you would have to modify the amp to accept another brand of terminals. If you need more assistance, or would like to inquire about repairing it, please visit my website at audioserviceclinic.com. You may contact me there. Thank you.

it is not passing it's self test. check the usual suspects (shorted output transistors, blown mini fuse, and that annoying pcb mount fuse in the power supply (looks like a resistor with one stipe)) if they all check out, test the relay coil for continuity. if it is open then replace the relay, but if it reads below 200 ohms the relay is ok, and i'd bring it to the shop for more extensive testing and repair.

As always with stereo amps the two channels are identical, so if one goes wrong you have the other as a control for testing purposes. So if you start by looking and comparing the two channels. that's a start! If a part looks odd on the faulty channel, but is fine on the good channel you have found the problem. You can also do tests, such as touching the two channels with an insulated screwdriver, while powered up. If it buzzers on the good channel, it should buzz on the other channel at that point. Keep away from the power supply and ignore anything that is on it's own, that has no duplicate, or is common to both channels.

Check the triac that is at the output

Check for shorted speakers, if ok check output transistors for short

That sounds like it could be a power supply issue to the main amp board. Possibly a voltage control regulator function issue?

Check power and fuses

check the fuse