No sound coming from my power amplifier gemini xga-4000

Question edited for a lot more clarity.
Question moved from Office Equipment.

Not much on it, but make sure vents are clear

https://www.google.com/search?q=xga+4000+protect+mode+reset

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Switch input connection pairs and if the 'fault' doesn't changes from one channel to the other it is almost certainly an amplifier or output fault.
Likewise switching the speakers. If after swapping the speaker connections the fault changes to the other speaker it is an amplifier fault. If not a speaker fault.

What kind of preamp and how are you using the xga, I assume on PA, and you want to use maybe a guitar preamp and amp head directly to it? Your preamp could go straight line in to the xga, the only thing the (whatever kind) of head is for power of onstage monitoring of your guitar. That is optional since the PA should have monitors. I personally use my full rig onstage to hear myself but, I mic it to the PA which always sounds better than direct. If you could be more specific to these models and uses or ideas, I could help you more.

Could be power supply related- failing capacitors being most likely.
Could also be PWM failure- Failing capacitors being the most likely.
Output may have shorted out, or the MOSFETS or IGBT's may have failed.

typically (unless your useing other gear besides mixer and amp) you'd come out of the L/R outs. ( Main outs ) to the Main inputs of the power amp then out to your speakers (outs of power amp). Now the amp could be in bridge mono or other factors but typically, like i said, just
Mixer Out- Amp In- Amp Out- Speakers.

A large amp like this likely has protection circuit (probably a relay) that doesn't connect the speakers until the amp is stable and balanced. You relly need the schematics for the amp.

Likely have damage in the amplifier... probably the output stage. It will require servicing.

It may NOT have a fuse. If too much power was sent or an amplifier drove DC to the speaker, the voice coil may have fried. The specs do NOT brag aboput protection, so it is likely either the speaker is blown or the internal wiring is broken. Open the unit and use an ophmmeter to tesst the speakers.

You connect POWERED speakers to the left and right outputs... You MUST use POWERED speakers or an external amplifier. This unit has a small headphone amp, but that CANNOT power passive speakers.

The output section of this unit appears to have a problem. That channel is in protect mode and will not produce sound. At this point, you should return this for a warranty repair. While relatively rare, this can happen with new equipment. As long as you have not overdriven the amp, the warranty should take care of the problem.

Keep us posted on how you make out.

Dan